240 



U. 8. P. R. R. EXP AND SURVEYS ZOOLOGY GENERAL REPORT. 



enters nearly five times. The origin of the ventrals is situated under the anterior margin of 

 the dorsal, as in A. obesa. The scales are next in size to those of A. bicolor. Seven rows are 

 found between the origin of the ventrals and the lateral line, and ten above it, making eighteen 

 rows in all. They are somewhat longer than deep, resembling in shape those of the foregoing 

 two species : the radiating grooves, however, are more numerous. The formula of the fins is 

 also much alike : 



D 2, 8 ; A 2, 8 ; C 6, 1, 9, 8, 1, 5 ; V 9 ; P 14. 



Metallic greenish brown above and on the sides ; beneath yellowish or whitish, scattered over 

 with small black spots. The fins are greyish olive. 



This species was collected in Mercede and Mohave rivers, by Dr. A. L. Heermann, under Lieut 

 R. S. Williamson, and is very closely allied to Lavinia gibbosa, Ayres (Proc. Cal. Acad. Nat. 

 Sc. I, 1855, 20), but, since I have no specimens of the latter, and that those before me measure 

 but five inches and a half, I feel reluctant to attempt an identification. 



List of specimens. 



LAVINIA, Girard. 



GEN. CHAR. The body is very much compressed, deep, sub-fusiform in outline, covered with well developed scales ; the 

 lateral line forming an opes curve, convex downwards, nearer the abdominal outline than the back. The fins are well developed ; 

 the insertion of the ventrals is situated either in advance of the anterior margin of the dorsal, or immediately under it The 

 posterior margin of the dorsal approximates more or less the anterior margin of the anal. The caudal is deeply furcated, 

 rounde upon its insertion, and provided with numerous well marked rudimentary rays above and below. The head is rather 

 small. The cleft of the mouth is situated altogether anteriorly to the orbit; it is of medium size, the upper jaw overlapping 

 the lower one, which is either rounded or truncated upon its symphysis. There are no buccal barbels. The eye is of moderate 

 size ; a narrow isthmus separates the gill openings. The pharyngeal bones are strongly curved, the upper branch directed 

 inwards and downwards, the inferior one slightly arched backwards, with the convexity dilated. The teeth are of the 

 cultriform kind of the grinding type, and disposed upon one single series of five, thus: 5 5, with a sharp terminal point. 



SYN. Lavinia, GRD in Proc. Acad. Nat. Sc. Philad. VII, 1854, 137; &, VIII, 1856, 184. 

 Acrocheilus, AGASS. in Amer. Journ. of Sc. 2d ser. XIX, 1855, 96. 



This genus, together with Orthodon and Algansea, includes some of the largest apecies of 

 Cliondrostomi so far observed in the fresh waters of North America, comparing well, in that 

 respect, with Chondrostoma and allied genera of the Old World. 



LAVINIA ALUTACBA,* (Acrocheilus alutaceus, Ag. & Pick.) from Williamette Falls and Walla- 

 Walla river, and collected by the United States Exploring Expedition, we have had no opportunity 

 to examine. 



*Proc. Acad. Nat. Sc. Philad. VIII, 1856, 184. 



