394 



SYNOPSIS OF THE CYPRINIDyE OF PENNSYLVANIA. 



the pakearctic genus the alimentary canal attains 2.5 the length, in Hybognathus 4 times, 

 while in Gymnostomus the length exceeds that of Campostoma, amounting to from 8 to 

 11 times the length (Heckcl). But in these genera it is arranged as in Chrosomus and 

 Stilbe, in a scries of horizontal convolutions in no wise affecting the position of the nata- 

 tory bladder. Indeed, in no other genus than Campostoma have I observed the latter 

 organ involved in vertical coils of the intestines, and separated from contact with the 

 abdominal walls. In C. dubium, sixteen coils may be counted from the side, each corre- 

 sponding to an intercostal space ; the intestine is eight and three-fifths length of head and 

 body. In C. hippops it is a little shorter. The natatory bladder in both is much dimin- 

 ished in size, not extending behind the anterior two-thirds of the abdominal cavity. This 

 is appropriate to the abode of the species, near the bottom, where they obtain their favor- 

 ite vegetable food. In the more numerous species of carnivorous habit, that rise to seize 

 insects on the surface, the bladder extends throughout the length of the abdomen. 



A distinct though less degree of shortening is seen in the genera Gymnostomus and 

 Hybognathus. Hybognathus nuchalis, Agassiz, the only known species of the genus, I 

 have found to be abundant in the Wabash lliver, and Dr. William A. Hammond presented 

 specimens to the Museum Academy Natural Sciences, from the Platte Paver, near Fort 

 Riley, Kansas. Its digestive canal is longitudinally folded, exhibiting six flexures. 

 The peritonaeum is black. 



The three epicystous genera above mentioned, and Acrocheilus,* x\g., of Pacific waters, 

 form a homogeneous group of lesser rank, partly coinciding with Professor Agassiz' 

 "Tribe Chondrostomi" (Amer. Journ. Sci. Arts, xix, 96), but which cannot be defined by 

 the structure of the lips, a feature which presents considerable modifications in the genus 

 Chondrostoma itself. To this group Prof. A. adds Exoglossum, Campostoma, Pimcphales,t 

 and Hyborhynchus. The first two genera have been already treated of; the two last I 

 have separated on account of the form of the dorsal fin. I therefore do not believe any 



* See Gill on this genus, Proe. Acad. Nat. Sei., 18G4. 



f Pimephales agassizii, sp. nov. 



Mouth short, terminal quite oblique, end of maxillary bone below nares, orbit one-fourth head 4.5 frontal 

 width. Head equal, greatest depth 4.5 to origin of caudal. From latter to origin first dorsal ray loss than from 

 latter to end of muzzle. Scales narrowly exposed, 8-9—44—5; 29 rows anterior to dorsal fin ; lateral lino extend- 

 ing to below dorsal fin. Radii D. 18. A. 7. V. 8. (I 19. P. 10, tip § to ventrals, latter to vent. Dorsal outline 

 arched; front depressed behind line of nares. Total length 2 inches 11 lines; end muzzle to anal 1 inch 8 lines. 

 Alimentary canal much complicated. Peritoneum with black pigment; above yellowish-olive, elsewhere dull 

 silver; dorsal fin dusky, especially in a spot on anterior rays. 



This species bears considerable resemblance to the P. milesii M., and the Hyborhynchus notatus Agass., and 

 points to the identity of the two genera. 



Habitat. A tributary of the Ohio at Richmond, Indiana. From a collection in Museum Academy, made by 

 Elijah Coffin at that place. 



