302 



U. S. P. R. R. EXP. AND SURVEYS ZOOLOGY GENERAL REPORT. 



List of Specimens. 



CLINOSTOMUS, 1 Girard. 



GEN. GHAR. Body elongated, compressed, sub-fusiform in profile. The head is compressed like the body, the frontal surface 

 being very declivous and sloping towards a pointed rostrum, so that in profile the head is sub-triangular, and, if broader, would be 

 wedge-shaped when seen from above. The mouth is very large, the lower jaw longer than the upper, beyond which it protrudes , 

 giving to the gape an obliqne direction upwards. The eye is very large ; the isthmus quite narrow. The dorsal fin is higher 

 than long, and placed between the ventrals and the anal, a little nearer the former than the latter. The caudal is deeply furcated. 

 The scales are of but moderate development, varying considerably in size between the different species. The lateral line forms 

 a downward curve upon the abdomen, so as to bring its conrexity nearer to the ventral than the dorsal outline. The pharyngeal 

 bones are rather slender, the lower limbs especially; a slight expansion may be observed upon their convexity; the upper limbs 

 being flattened, bent inwardly, and either shorter or of equal length with the lower limbs. The teeth are of the raptatorial Hnd, 

 of the hooked type, without grinding surface, and disposed thus: 2 | 4 4 | 2, or 2 | 5 4 | 2, and sometimes 1 | 4 4 [ 2. 



SfK.Ciinostomus, GRD. in Proc. Acad. Nat. Sc. Philad. VIII, 1856, 211. 



This genus is more closely related to Ptycliocheilus than to any other of the family. The 

 pharyngeal teeth are constructed upon the same pattern ; the chief difference being found in 

 the inclined gape of the mouth, and the protrusion of the lower jaw beyond the upper. 



Its typical species is Luxilus elongatus of Dr. Kirtland, Leuciscus elongatus of other writers^ 

 Leuciscus product us of Dr. Storer. 



Three other species have been characterised, one of which inhabiting the Potomac river (C. 

 funduloides) , another James river, Virginia (G. qffinis); the third one (G. carolinus) was collected 

 at Salem, North Carolina. (See Proc. Acad. Nat. Sc. Philad. VIII, 1856, 211.) 



Family CYPEINODONTIDAB , Owen. 



The upper arcade of the mouth (upper jaw) is formed exclusively by the premaxillar bones, 

 as in the Cyprinoids. Both jaws are provided with teeth, which the latter have not. The 

 pharyngeal teeth, the upper as well as the lower, are card-like, thus differing widely from those 

 of Cyprinoids. The gill apertures are continuous under the throat, whilst in Cyprinoids they 

 are separated by an isthmus, varying in width, according to the genera. The bony process at 

 the base of the cranium, so characteristic in Cyprinoids, does not exist in the present family, 

 The swimming or air bladder is simple, and not connected with the organ of hearing by a chain 

 of small bones. The pseudo branchia are wanting. Their stomach is without cul-de-sac, and the 

 pylorus without appendages. The majority are ovo-viviparous, in which case the eggs are 

 retained in the abdominal cavity until hatched. 



In most fishes of this family, if not in all, the upper surface of the head is protected by scales 

 or plate-like scales, irregular in their outlines, and variable in size. 



1 A genus Clinostomum was instituted in the class of worms, with a few weeks priority, hence did not come to our knowledge 

 till after the publication of the present one. As matters stand, there is no impropriety in preserving both in their respective 

 classes. 



