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



DIOPLITES, Rafin. 



Gex. Char. — Body elongated, sub-fusiform in profi e , compressed. Head well developed. Preoperclc smooth and entire. 

 Moull: liirge ; lower j-iw longest. Velvet-like teeth on the jaws, front of vomer, and palatine hones. Tongue smooth. Checks 

 and opereular apparatus scaly. Branchial apertures continuous under the throat. Two dorsal fins contiguous upon their base. 

 Three small anal spines. Insertion of ventrals on a line immediately behind the base of pectorals. Caudal fin posteriorly sub- 

 crescentic. Scales well develiped and posteriorly ciliated. 



Siv.—Diopliles, R.afin. Ichth. Ohiens 1820, 35. 



Grystes, Cov. &. Val. Hist. Nat. P iss. 1I[, 1829, 54. 



The fishes of this genus are not uncommon in the localities where they occur. They resemble, 

 in general appearance, the common or yellow perch, though often reaching a much larger size. 

 They are esteemed as an article of food, and known under the general appellation of " trouts " 

 or " hass." Exclusively of frosh water habits, they are met with in ponds and rivers, asso- 

 ciated with various kinds of suckers, chubs, daces, minnows, &c., upon which they ieed. 



They are remarkable in the percoid family for their general smooth appearance, having 

 neither spines nor serratures upon the opercular apparatus. The scales themselves are but 

 slightly pectinated, and the few pectinations are quite deciduous or falling off with the 

 epidermis. Their teeth are all uniform and velvet-like, and exist upon the palatine bones as 

 well as upon the vomer, premaxillaries (upper jaw), and dentaries (lower jaw). The mouth 

 is generally large, with its gape slightly oblique upwards, and the lower jaw protruding beyond 

 the upper. The tongue is generally smooth anteriorly, but an elongated and narrow patch of 

 velvet-like teeth is occasionally observed upon the middle line at the base of that organ. 



A feature peculiarly characteristic of this genus, when associated with its other natural 

 characters, consists in the separation of the spinous portion of the dorsal from the soft portion, 

 by a wide gap, so that we have in reality two fins, contiguous upon their base only. This fea- 

 ture appears to constitute the chief difference between DioplUes and Calliurus, not taking into 

 account the general aspect of the body, which has a subordinate value. 



The species enumerated below appears to be very common in Texas, and even south of the 

 Rio Grande del Norte (Rio Bravo), as proved by the specimen collected by Lieutenant D. N. 

 Couch, United States army, in the Rio San Juan, near Cadereita, province of New Leon. 



We have examined two immature specimens of another species — perhaps D. salmoides ; one 

 collected at New Braunfels, Texas, by Dr. Lindheimer, the other in the Rio Brazos, Texas, 

 by Dr. G. C. Shumard, and which must await another opportunity for a more critical 

 determination. 



DIOPLITES NUECENSIS, Grd. 



Tront, or River Bass. 



Spec. Chab. — Body elongated, sub-fusiform. Head constitutinga little less than the third of the entire length. Posterior extremity 

 of maxillary extending to a vertical line drawn posteriorly to the orbit. Scales on the cheeks nearly equal in size to those on 

 the gill covers. Origin of vcntrals posterior to the bsse of pectorals. Upper regions reddish brown, maculated. A lateral dark 

 band. Inferior regions whitish, unicolor. 



Stn.— Gr!(,'i(es Ji«frfnci«, B. & G., in Proc. Acad. Nat. Sc. Philad. VII, 1854, 25. 

 Troul, or Jiiver Hass, Vernacular. 



A full description and a figure of this species will be found in the Ichthyology of the United 

 States and Mexican Boundary Survey. 



It is closely related to, if not identical with, Grystes nobilis, Agass., from the southern bend 



