A third species occurs in the Gulf of Mexico. It is distinguished by its larger head and fins and other characters. It appears to have never been described, and, for this form, the name of Brevoortia patronus is proposed. It is accompanied by the same crustacean parasite that is found in the mouths of B. tyrannus, to which Latrobe gave the signifi. cant specific name of prægustator.

C.-DESCRIPTIONS OF THE AMERICAN SPECIES OF MENHADEN, WITH ANATOMICAL AND PHYSIOLOGICAL NOTES.

7.-TECHNICAL DESCRIPTIONS.

Brevoortia tyrannus.

40. The following is a careful description of the common menhaden, which occurs on the east coast of the United States and Brazil: Brevoortia tyrannus (Latrobe) Goode. THE MENHADEN.

Diagnosis.-Head and jaws short; the length of the head less than one-third of the length of the body less the caudal fin; especially short in subsp. aurea, the maxillary in length much less than three-twentieths of the length of the body.

Height of body about one-third of total length, in very fat individuals about three-eighths. Fins comparatively short, the height of the dorsal less than length of maxillary, and considerably less than three-tenths of length of body; that of the anal usually less than half that of maxillary; that of ventral always less than one-tenth of total length; the length of middle caudal rays one-fifth that of body, and less that of exterior caudal rays, usually about three-fourths, often less than two-thirds, and rarely more than five sixths of total length. Fins all shorter in subsp. aurea. Insertion of ventral far behind tip of pectoral. Insertion of dorsal about equidistant from snout and base of middle caudal rays, but varying two or three one-hundredths to either side of this median point, and always slightly behind the vertical from insertion of ventral.

Scales of medium size, much serrated, arranged very irregularly in 24-26 transverse and 60-80 longitudinal rows. Scales forming sheath at base of pectoral not large. Squamation of caudal lobes moderate. Operculum strongly striated in subsp. menhaden, almost smooth in subsp. aurea. Scapular blotch conspicuous.

This species is easily distinguished from Brevoortia patronus by its shorter head and fins, by its slender body and its pectinated scales, and from B. pectinata by its smaller, less regularly arranged, and more numerous scales, and its shorter, less furcate caudal fin.

Individual variations and special descriptions.

Head. The length of the head varies from 28 to 33 hundrdths of total length. The posterior end of the maxillary extends to a point in the vertical from the centre of the orbit. The length of the skull, as

indicated by the "distance from snout to nape," varies from .19 to .23. The length of snout, measured from a line drawn perpendicularly through the centre of the orbit, varies from .09 to .11. The length of maxillary varies from .12 to .14; that of mandible from .15 to .18. The diameter of the eye enters 43 times in the length of the head; its width varies from .11 to .15 in very fat individuals.

Shape of body.-This is exceedingly variable, and the variation is caused largely by the fatness of the individual. In very plump ones, the expansion of the belly throws back the origin of the ventrals and anal, and greatly changes the appearance of the fish. In the specimens before me the height of the body ranges from .31 to .383. The table of measurements subjoined shows the effect of increased height of body upon the other measurements of proportion.

Fins.-The range of variation in the position of the dorsal is indicated in the diagnosis. There is no appreciable correlation between the positions of the dorsal and anal in the same specimen. The insertion of the anal is distant from the snout from .68 to .75. The length of the rays in dorsal, anal, ventral, and caudal vary much, as the table of measurements indicates. In the caudal the upper lobes vary from .16 to .25, the lower lobes from .18 to .27. The relation of the pectoral and ventral fins is much affected by the length of the head, the insertion of the former being thrown much farther back in long-headed individuals.

Scales. The degree of serration varies much in individuals as well as the squamation of the bases of the vertical fins, and the number and regularity of the body-scales. In young individuals the scales are arranged with much regularity, but in the adults I have strong reason to believe that other scales are intercalated here and there throwing the arrangement into great disorder and rendering an accurate enumeration impossible.

Subspecies.

The series before me embraces some two hundred specimens of Brevoortia tyrannus of various ages, seasons, and localities. Almost every feature is subject to wide variations, and there is usually no decided correlation between different characters except that a long head is accompanied by long jaws and a pectoral set farther back and extending more nearly to the insertion of the ventral. There are, however, certain groups of individuals which can be included within a diagnosis, which may serve to distinguish them from all the others of the same species. To what extent it is desirable to define varieties which are not separated geographically, I am not well satisfied. The exact meaning of the terms "sub-species" and "variety," as employed by Cope, Coues, Gill, Yarrow, and other recent writers, has not been definitely interpreted. It seems desirable, however, to designate in some way the limits of variation from the normal specific types in different directions. With this purpose, and remarking that by a subspecies I mean simply a divergent form connected by intermediate forms with the typical specific form, I have

thought it desirable to name provisionally two varieties, and to call attention to others which may possibly exist. This is done with much hesitation, and only with a view to an attempt to formulate the minor differences to be observed between fish of the same species on different parts of our coast. A precisely parallel case is to be found in the shad of the different Atlantic rivers, which are well-known to exhibit strong distinctive marks. Very possibly every school of menhaden has its own characteristics. In every case where I have had an opportunity to observe them, the individuals composing the same school were closely similar to each other.

The typical form of the species, as now defined, is taken from the coast of Southern New England and the Middle States. It has the height of the body about one-third of the total length, the head three-tenths of the total length, or a little more; the maxillary long (.14 to .144), and exceeding the height of the dorsal.

The species described by Spix, under the name of Clupanodon aureus, cannot be distinguished by any apparent specific characters from Bre-aurens voortia tyrannus, since one or more of the specimens of the latter species has 50 before me partakes of some of the peculiarities of the Brazilian form. re gill There is, however, a general average of character exhibited by the Brak. zilian specimens, as well as the figure of Spix, with which they closely agree, which seems to me to entitle them, for the present at least, to recognition as belonging to a distinct geographical race. The distinctive characters appear to consist in (1) a greater average height of body; (2) a lesser length of head; (3) a lesser average length of maxillary and mandible; (4) a slightly lower anal and dorsal fin; (5) a greater average distance of anal from snout; (6) a greater average length of the medial caudal rays; (7) a shorter average length of pectoral; (8) a more regular arrangement of the scales, and a more luxuriant growth of small scales at the basis of the fins.

A number of specimens from Noank, taken in 1874, vary quite as much from the normal type, and in almost the same respect as the variety just described. The maxillary and mandible are shorter, however, than in the Brazilian form, the anal fin lower and the lobes of the caudal are extremely short, sometimes hardly exceeding in length the pectoral fin. But for the fact that these specimens show almost all the characters of the Brazilian Brevoortia, and in some cases exaggerations of them, I should be inclined to consider the aurea a distinct species. Having with some hesitation allowed to this the rank of a subspecies, the question must be decided as to the propriety of also allowing subspecific rank to this peculiar form from Noank. The exact meaning of the terms subspecies and variety, as recently employed by zoologists, is not very clear to my mind, but I infer a "subspecies" to be composed of an assemblage of individuals varying uniformly from the typical specific forms in a degree sufficient to be susceptible of description and definition, though not necessarily separated from it by the absence of

connecting forms. Premising, then, that in giving to the Noank specimens a subspecific name, my object is simply to define the limits of variation from the normal type in a given direction, I would provis ionally propose that they be designated as subspecies brevicaudata.

The specimens from the Saint John's River, Florida, are extremely variable in every respect. Certain individuals show a tendency to elongation of the head and fins, and also a slenderness of the posterior part of the body, and nearly all the individuals from that region are more lightly and gracefully shaped; they all have a tendency to a yellow coloration, especially upon the caudal lobes. I have not felt justified, however, in calling it a subspecies.

I have not had an opportunity to study the Maine schools, but am inclined to believe that their differences are very perceptible.

In plate VI are shown the chief variations of form. Fig. 1 shows the typical form; fig. 2 the subspecies brevicaudata; fig. 3 the average form from the Saint John's River, Florida; fig. 4 the subspecies aurea.