1854.J 



137 



Genus LAVINIA, Girard. 



Mouth shaped as in Gila and Pogonickthys, but proportionally smaller 

 than either and unprovided with barbel. Body covered with large scales 

 as in Pogonichthys. The genus Lavinia, therefore, is intermediate between the 

 two above mentioned. 



20. Lavinia exilicatjda, B. and G. Body compressed, swollen upon its middle 

 and tapering towards both extremities. Tail more particularly attenuated. 

 Greatest depth, in advance of the dorsal, contained about four times in the length, 

 which is eleven inches, and in which the head enters five times and a half. The 

 mouth is very small ; its am>le being far from reaching the anterior margin of 

 the orbit. The eye is circular and rather below the medium size ; its diameter 

 being contained nearly six times in the length of side of head. Isthmus very 

 small; branchiostesal rays three on either side. Anterior margin of dorsal 

 equidistant between the extremity of snout and tip of central rays of caudal, 

 which latter fin is deeply forked. Base of anal longer than that of dorsal but 

 considerably lower, particularly upon its posterior third. Insertion of ventrals 

 in advance of the anterior margin of dorsal. Pectorals rather small. 



D II. 12. A It 14 or 15. C 7. 1. 8. 8. 1. 7. V I. 19. P 17. 



The scales are rounded and very thin. The lateral line, in which there are 

 about sixty scales, forms an open curve on the abdomen with a downwards 

 convexity much nearer the insertion of ventral than base of dorsal fin. 



Reddish brown above, silvery grey on the sides, the scales being provided 

 with minute crowded dots upon their margin. Beneath yellowish with scales 

 unicolor. Fins yellowish grey. 



From Sacramento River, Cal. 



21. Lavinia crassicauda, B. and G. The body in this species is less deep in 

 the middle and less attenuated behind than in L. exilicavda. The peduncle of the 

 tail is largely developed and contrasts greatly with that of the latter mentioned 

 species. The head and mouth are proportionally larger ; the former being con- 

 tained four times and a half in the total length ; and the cleft of the second, 

 although not reaching the anterior ed^e of the orbit, extends, nevertheless, farther 

 backwards than in L. exilicauda. The greatest depth is about equal to the length 

 of head. The eye is subcircular, and its diameter contained about six times in 

 the length of side of head. The caudal is less emarginated posteriorly, and 

 the insertion of ventrals situated almost under the anterior margin of the dorsal. 



D II. 9 A II. 9. C 9. 1. 9. 8. 1. 8. V I. 9. P 17 or 18. 



The scales are much larger than in L. fx/licauda,and the course of the lateral 

 line similar, being composed of about fifty-five scales. The general coloration 

 is the same. 



Specimens were procured at San Francisco, in the Rio San Joaquin, and several 

 tributaries of that basin. 



22. Lavinia conformis, B. and G. Only one specimen of this species was 

 obtained; its total length being about four inches. It is related to L. crassicav- 

 da, having like it a much more compact tail than L. exilicauda. The general 

 appearance of the fish is suggestive of L. crassicauda; the body is deeper and 

 proportionally less elongated ; the eye much smaller and the scales larger. Ano- 

 ther distinctive mark between the two species consists in the position of the vent- 

 rals, the insertion of which in L. conformis, is situated in advance of the an- 

 terior margin of dorsal, whilst it is placed slightly behind it in L. crassicauda. 



D II. 9. A II. 9. C 6. I. 9. 8. I. 6. V I. 8. P 16. 



Purplish brown above, light on the sides ; belly and head, beneath, dull yellow- 

 ish. 



From Posa creek, San Joaquin basin, Cal. 



23. Leucosomus occidentalis, B. and G. Numerous immature specimens of 

 this species were collected, together with one about five inches in length. The 

 body is very much compressed, deepest upon the middle of its length and taper- 

 ing towards both extremities. The greatest depth is contained four times in the 



