﻿ELONICHTIIYS. 



47 



Genus — Elonichthys, Giebel, 1848. 



Amblypterus (pars), Agassiz. 



— (pars), Egerton. 

 PaLjEOMSCUS (pars), Agassiz. 



— (pars), Egerton. 



— (pars), Jackson. 



— (pars), Newberry. 

 Pygopterus (pars), Agassiz. 

 Elonichthys, Newberry. 



The body is fusiform, sometimes rather deep j the tail is large ; the caudal fin deeply 

 cleft, very inequilobate, the upper lobe prolonged. The dorsal fin is situated well 

 forward, nearly opposite the interspace between the ventrals and the anal ; both dorsal 

 and anal are large, triangular, of numerous closely set and closely jointed rays. The 

 pectorals and ventrals are acuminate, the base of the ventrals not extended ; their rays 

 are also very closely jointed, except at the commencement of the first few rays of the 

 pectoral. The fulcra of all the fins are closely set, but very minute, usually requiring 

 the aid of a lens to distinguish them ; the V scales of the upper margin of the tail are, 

 however, well developed. The scales are of moderate size, rhomboidal ; those of the 

 flank are slightly higher than long, with concave upper and convex lower margin ; 

 they get lower and narrower towards the belly, and diminish generally in size 

 posteriorly, getting also more equilateral towards the tail. The anterior overlapped 

 portion of each body-scale is very narrow, a mere margin in fact ; the exposed area is 

 brilliant, and variously ornamented with striae, or coarse punctures, or both ; the posterior 

 margin is often crenulated or serrated. In many cases the scales become smooth or 

 nearly so on the tail. There are specially large scales in front of the origin of the dorsal 

 fin, and in front of the anal, in the region of the vent. The suspensorium is very 

 oblique, and the gape very wide ; the operculum is well developed, oblong ; the inter- 

 operculum quadrate; but, as in Pcdceoniscus, &c, there is no suboperculum. The 

 branchiostegal plates, or rays, are numerous, sometimes numbering as many as twenty- 

 two {B. semistriatus) on each side ; in some other species the number is much smaller, but 

 I feel reluctant on that account to multiply the number of genera. There is a rhomboidal 

 median plate behind the symphysis of the jaw ; and the anterior one of each lateral 

 series is much broader than the rest. The jaws are stout, the teeth acutely conical, 

 sharp, enamel-tipped, of two sizes, large and small, the large ones being placed in a row 

 internal to the more closely set outer row of small ones. The ornament of the cranial 

 bones is usually more or less tubercular ; the facial bones and those of the shoulder- 

 girdle are striated ; the jaws are, however, tuberculated just at the dental margin, the 

 tubercles appearing sometimes to pass insensibly into the outer row of minute teeth. 



