68 U. S. p. R. R. EXP. AND SURVEYS — ZOOLOGY GENERAL REPORT. 



HEMILEPIDOTUS SPINOSUS, A vies. 



Smc Chab. — Upper surface and sides of head provided with membranous flaps. Eye quite large. Posterior free extremity 

 of maxillary extending to a vertical line drawn across the poBterior rim of the pupil. Dorsal band of scales c< mposed of six 

 rows or series ; lateral band, of seven, five below and two above the lateral Hue. Ground color dark reddish brown, with 

 darlier transverse bands and blotches. 



Sis.—HemUqndotm sjmosiui, Ayrks, MSS.— Grd. Proc. Acad. Nat. Sc. Philad. VIII, 1856, 134. 

 CahjcilcpiiJotus fj)inosus, Ayres, Proc. Cal. Acad. Nat. Sc. I, 1855, 76. 



The head in this species constitutes the third of the whole length, not including the caudal. 

 It is depressed, hroader than deep, grooved between the orbits, slightly depressed upon the 

 skull, and covered with small spinous processes and membranous flaps. A fringed pair of the 

 latter (one on each siile) may be observed upon the occipitals, the upper and posterior rim of the 

 orbit, the upper angle of the opercle, and upon the cheeks. A similar, but not fringed, flap is 

 seen at the posterior free extremity of the maxillary. A narrow and rather elongated pair exist 

 upon the chin near the symphysis of the dentaries. The eyes are large, sub circular, and slightly 

 turned upwards ; their longitudinal diameter enters about three times and a half in the length 

 of the sides of the head, and not quite once in advance of their anterior rim. The interocular 

 space is narrow. The anterior nostril is tubular and nearer to the eye than the extremity of 

 the upper jaw. The turbinals are conspicuously spinous ; the snout blunt and rounded. The 

 posterior extremity of the maxillaries extend backwards to a vertical line drawn posteriorly to 

 the pupil. The limb of the preopercle is provided with four spines ; the two uppermost being 

 the largest and more close together than the remaining two, which occupy the inferior branch of 

 that bone. The preopercle exhibits two spines — an elongated one, buried in its upper margin, 

 and another rather short, at the inferior angle of the same bone. The branchial apertures are 

 separated under the throat by an isthmus, the width of which is contained about five times in 

 the distance, comprised between its edge and the extremity of the lower jaw. The branchioste- 

 gals are six on either side, the inferior one being rather small and slender. 



The body, anteriorly, is almost as wide as deep ; it becomes, however, soon compressed pos- 

 teriorly, so as to be deeper than broad. The profile is sub-fusiform in specimens of medium size. 



The origin of the anterior dorsal fin is situated in advance of a vertical line intersecting the 

 base of the pectorals. It is composed of eleven spinous rays distributed over a space some- 

 what less than the half of the base of the second dorsal. The three first rays are nearly equal 

 and shorter than the fourth and all the succeeding ones, except the two last ; it results from 

 this structure that the outline of the fin is depressed between the third and fourth rays. The 

 second dorsal is contiguous to the first at their bases ; it is composed of twenty articulated but 

 undivided rays, constituting a fin higher than the anterior, and extending to very nearly the 

 base of the caudal, for, the tips of the terminal rays overlap slightly the insertion of the caudal 

 rays. The caudal itself is rather small, rounded, or sub-convex upon its posterior margin, and 

 contained six times and a half in the total length ; it is composed of nine bifurcated and two 

 undivided rays and rudiments of rays. The origin of the anal is situated opposite the fifth 

 ray of the second dorsal ; it is not quite so deep as the latter is high, and does not extend quite 

 so far posteriorly. The sixteen rays of which it is composed are all undivided, the interradial 

 menibtane being deeply emarginated. The insertion of the ventrals takes place immediately 

 opposite the upper portion of the base of the pectorals ; they are elongated and slender, com- 

 posed of four soft and one spinous rays, the extremities of which do not reach the vent. The 



