190 



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



purple. The dorsal, caudal, and pectorals are dark greyish olive ; the rays of the anal and 

 ventrals are olive, whilst their interdigital membrane is purple. 



A specimen, fourteen inches in total length, was caught in Tomales Bay, California, by E. 

 Samuels. 



Plate XL, fig. 1, represents Rliacocliilus toxotes, somewhat reduced in size. 



Fig. 2 is a scale from the dorsal region. 



Fig. 3, a scale from the lateral line. 



Fig. 4, a scale from the abdominal region. 



List of specimens. 



IIYSTEROCAUPUS, Gibbons. 



GEN. CHAR. Head is small or of medium size. Mouth small, gape slightly oblique ; jaws sub-equal. Lips rather thin ; lower 

 one free all round. Premaxillaries quite protractile. Teeth sub-conical, occupying the fore part of the jaws only, and disposed 

 upon one single row. Spinous portion of dorsal much longer and somewhat higher upon its middle than the soft portion. 

 Anterior articulated rays of anal simple, and preceded by three small spines. Caudal fin furcated. Branchiostegals, five on 

 either side. Scales large. Lateral line concurrent with the dorsal outline. No scales upon the fins. Dorsal groove running 

 nearly along the entire base of the fin ; sheath formed of one row of scales only. 



SYN. Hysterocarpus, GIBBONS, in Proc. Acad. Nat. Sc. Philad. VII, 1854, 124. 



This genus bears a general resemblance to Abeona, Ennichthys, and Holconotus, by the outline 

 of its dorsal fin, the spinous portion of which is higher upon its middle than the highest articu 

 lated rays. It differs, however, from them by that same spinous portion of the fin being much 

 more extended than the soft, which constitutes only a fraction of the entire base or length. 

 From Enniclithys and Holconotus it furthermore differs by the presence of one single row of teeth 

 upon the jaws, instead of two. The base of the anal fin is also shorter. The anterior articu 

 lated rays of the anal are simple, whilst they dichotomise in Abeona, Ennichthys, and Holconotus. 

 Its affinities with Abeona are apparently closer, since there is but one series of maxillary teeth ; 

 still the lower lip is free all round as is the case in Enniclitliys and Holconotus, whilst it is 

 attached by a frenum to the pymphysis of the jaw, as in Abeona. From the latter it may yet 

 be distinguished by a shorter caudal peduncle. 



HYSTEROCAEPUS TRASKII, Gibbons. 

 PLATE XXVI, FIG. 14. 



SPEC. CHAR. Body sub-elliptical in its profile ; nape convex, frontal line depressed. Eye circular, of medium si/e. Posterior 

 extremity of maxillary extending to a vertical line drawn in advance of the anterior rim of the orbit. In the male the upper 

 regions are dark or purplish brown, unicolor ; yellowish olive, spotted with black, on the lower portion of the sides ; throat and 

 belly yellowish golden. In the fema e the back is ash-colored, with irregular black patches, approximating somewhat to inter 

 rupted bands, across the sides ; belly lemon yellow. 



S VN . Hy.iterocarpns traskii, GIBBONS, in Proc. Acad. Nat. Sc. Phi ad. VII, 1854, 105 & 124. GRD. in Proc. Acad. Nat. 

 Sc. Philud. VIII, 1856, 13G. 



