34 



snout to the nape, thence arching very slightly, 

 the line of union of the head and body not mark- 

 ed by any depression or change of form. The 

 greatest depth contained not quite five times in 

 the total length. Length of the head a little 

 • greater than the depth of the body. Depth of 

 the head at the plane of the eyes equal to the 

 distance of the same plane from the suout. 



Mouth oblique, gape tolerably free, the plaue 

 o( the tip of the maxillary passing about mid- 

 way between the nostrils and the eye. Lower 

 jaw the shorter. Lips smooth, a little loose and 

 fleshy, not corrugated. Each jaw provided with 

 a firm, thickened layer, placed along the inner bor- 

 der of the lip; this layer is narrow, and becomes 

 more attenuated as it passes back along the jaw 

 until, before reaching the angle of the mouth, it 

 ' terminates; it is whitish, with a slight tendency 

 to plication transversely; its connection with the 

 mucous membrane both of the roof of the mouth, 

 and of the lips is feeble, so that it is quite easily 

 detached ; it corresponds to the lips of the Suck- 

 ers, though the structure of the month is not at 

 all like that of these fishes. No traces of. bar- 

 bels are discernible. 



Eyes very nearly circular, their diameter con- 

 tained a little more than seven times in the length 

 of the head. 



Posterior aperture of the nostrils much the 

 larger, nearly circular,- covered by a crescentic 

 flap from its auterior border. 

 ,, . . 'f 'he ■ posterior superior and posterior iuferior 

 borders of the operculum meet at nearly a right 

 angle, but as the suboperculum continues the bor- 

 der of the opercular apparatus from this point, 

 this border becomes nearly a regular curve, only 

 slightly angulated. 



Scales of moderate size, not varying much in 

 dimensions on different parts of the body, about 

 eighty two along the course of lateral line, and 

 seventeen in an oblique line above it at the origin 

 of tli- dorsal fin. Scales oval, not much angula- 

 ted; concentric lines very fine; radiating lines 

 of the posterior portion numerous, encroaching 

 somewhat on the lateral portions. Those form- 

 ing the lateral line have the tube commencing 

 near their anterior border. 



The dowU fin, trapezoidal in form,, arises at a 

 . -..,. point a little nearer to the snout than to the tip 

 of the central caudal rays. Its length is equal 

 to the depth of the head at the plane of the pu- 

 pils! its height is a little greater, the fourth ray 

 (which is simple, articulated) being the highest 

 and, just double the height of the last ray ; the 

 first two rays arc very short. 



The vi-iit r.ils. arising a little in advance of the 

 dorsal, which they equal in height, are rounded. 

 Their.tip does not quite reach ihc vent. 



The mud, similar to the dorsal ia form, is a 

 little less in bolh leimlh and height. It an 

 little iu advance of the pouiUto whieh the rays 



of the dorsal reach. The fourth ray, branched, 

 is the highest, the first being very short. 



The pectorals, rounded, have a height equal to 

 the distance from the origin of the.ventrals to 

 that of the anal. 



The caudal is beautifully waved on its posteri- 

 or margin, each lobe being convex. The height 

 of the central rays is half that of the external. 



D. 3-8; A. 2-8; V. 1-9 ; P. 17 ; C. 19. with 

 eight or nine accessories. 



Color dark greenish brown above, becoming 

 lighter on the sides, abdomea white. 



Lateral line convex downward; passing, pearer 

 to the ventral fin than to the dorsal. A -similar 

 row of tubes is continued forward from upper 

 angle of the branchial- aperture, descends behind 

 the eye, turns forward beneath it, and occupies 

 the entire length of the chain of suborbital bone-'. 

 Another row, imperfectly manifest, crosses the 

 top of the head, at its line of. junction with the 

 body. 



M. robmtus appears to be by no means com- 

 mon. It is brought to market from the San 

 Joaquin, in company with G da grandis from 

 which it is not distinguished by the fishermen, 

 both being sold under the singularly inappropriate 

 name of Salmon Trout. It lias in fact much re- 

 semblance in external characters to that species, 

 though the body is stouter, aud the head relati\e-- 

 ly larger not being concave on its dorBal surface 

 and as it were separated from the body. In con- 

 tour it is quite like the Dace of the Connecticut 

 River, (Leueiscus pulchellus; Storer.) But it is 

 readily removed from these species, and from 

 every other Oyprinoid hitherto described, by the 

 structure of the teeth on the iuferior -pharyngeal 

 bones. The bones themselves are short , -strongly 

 curved, and very stout; somewhat resembling iu 

 form those of L. ptdcheltus already mentioned, 

 though much more robust than those of any oth- 

 er (Jaliforniaii type of- this -family. The "teeth 

 are arranged in two rows. Those of the external 

 row are four (in some. instances five) ittnurober, 

 remarkably thick and strong, tether- sho^t, each 

 provided with a broad enamelled crown which is 

 truncate obliquely inward, thas affordingta-large 

 smooth grinding surface ; they are •closely placed, 

 the crowns nearly touching each other. I The in- 

 ner row is but an anperfect one; consisting*! two 

 teeth, or at the most. three, which art, stnattf with 

 their crowns blunt, but not; truncate :asia the 

 outer row. 



We find in th)3- formation an-intenwadiate 

 condition between, that of the- open -mouthed 

 (Jyprinidac, and that of the tribo of Gateatomi. 

 We have the pharyngeals, tbft^mall jj«mber of 

 teefth with their nearly cylindrical hediee^hich 

 represent the former,. while we have ala© the ab- 

 ruptly truno&te&aunwiite which occur iu the lat- 

 ter. And as aafrther- illustration of themi^Bsage 

 toward the (Jatostoini we have tbe thiukeoied de- 



[ March 12.] 



