284 



U, S. p. R. E. EXP. AND SURVEYS — ZOOLOGY GENERAL REPORT. 



List of specimens. 



HUDSONIUS, Girard. 



Gen. Char. Body elongated, cnmpresEed, fusiform in profile, and covered with quite large scales. The lateral line being 



nearly median. The head is of but moderate size ; the snout being sub-conical and rounded anteriorly. The mouth is sub- 

 terminal, somewhat protractile, in which situation it is directed obliquely forwards and downwards ; when shut, the lower jaw 

 fits within the upper, the snout being slightly protruding. There are no barbels about the mouth. The eyes are large ; the 

 isthmus is small The dorsal is higher than long ; its anterior margin is even with the insertion of the ventrals. The anal has 

 a proportionally longer base than the dorsal. The caudal is deeply furcated. The pharyngeal bones are well developed ; the 

 mferior limb is rather short, its extremity being flattened and slightly turned outwardly. From the middle of the convexity a 

 sudden expansion occurs, tapering into the upper limb, slightly curved downwards. The teeth are of the bruising kind, of the 

 hooked type, provided with a grinding surface. But there occur many irregularities, being more or less hooked and the grinding 

 surface more or less developed. It is not uncommon to observe all these variations upon ihe pharyngeal of a single specimen. 

 The teeth are disposed upon a double row with the following variations : 2 | 4—4 ] 3 ; 2 | 4—4 | 1 ; | 4 — 4 | 2, or | 4—4 | 1. 



SvN.— //wrfsonms, Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 210. 



The type of the present genus is Clupea hudsonia, De Witt Clinton, Leuciscus hudsonius of 

 more modern writers. This species occurs as far northwest as Lake Michigan and in the fresh 

 waters of Illinois and Wisconsin. 



A second species was detected in the hrackish waters of Chesapeake bay and described under 

 the name of Hudsonius aTnarus.—{See Proc. of the Acad, of Nat. Sc. of Philad. VIII, 1856, 210.) 



GILA, B. & G. 



Gen. Char. — Body sub-fusiform, compressed, with the back more or less arched, especially in large and old specimens, and 

 Bometimes tapering very much posteriorly, with the peduncle of the tail very slender. The head being depressed and 

 proportionally small, with its upper outline often concave ; the snout is elongated ; the eyes are of moderate size ; the isthmus 

 small. The mouth is of medium size, the upper jaw overlapping the lower, so as to conceal its cleft from above. No barbels, 

 or rudiments of barbels. The branchiostcguls are three on either side. The ventral fins are inserted in advance of the 

 anterior margin of the dorsal, and the anal posteriorly to the base of tlie dorsal. The caudal is furcated. The scales are 

 small on the dorsal region and of medium size on the sides, and longer than deep. The lateral line forms an open curve along 

 the middle of the abdomen. The pharyngeal bones are well developed, the inferior limb elongated, the upper one forming an 

 open curve ; the convexity being somewhat exp.inded, the expansion tapering along the upper and inwards limb. The teeth 

 are well developed, of the raplatorial kind of the hooked typo, A'ilhoul grinding surface, sub-cylindrical, slightly compressed, 

 and disposed upon a double row of one or two and four or five as follows : 1 | 4—5 | 2, or else 2 | 4—5 | 2. 



Stn.— Gi(a, B. & G. in Proc. Acad. Nat. Sc. Philad. VI, 1853, 368 ; &, in Sitgr. I'xpl. of Zuni & Color. Rivers, 1853, 

 148 —Grd. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 205. 



Prior to our " researches upon the Cyprinoid fishes inhabiting the fresh waters of the United 

 States west of the Mississippi valley,"* the genus Gila was still composed of heterogenous 

 elements. Two of our own species originally placed in it have gone, with some other new 

 species, to form the genus Tigoma. A third and a fourth species, described by Dr. Ayres, have 

 likewise been removed elsewhere ; the former going into the genus Ptychochdlus associated with 



•See Proceedings of the Academy of Natural Sciences of Philadeli>hia, vol. VIII, 1856. 



