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DESCRIPTION OF TWA FOSSIL liEMAINS. 67 



FJianeropJeuron—TlvxhEY (Glypticus — Agassiz.) {Nov. Gcnns.) Pl. V. VI. 

 Phatieropleuron Andersoui — Huxley. (Nov. Species.) 



Of this new genus and species of Devonian fish, several fragments, now in 

 the Museum of Practical Geology, have been sent to me by Dr. Anderson ; but 

 the most complete specimen, figured in Plate VI., is in the collection of the 

 British Museum, where it lies in the midst of a group of fish which have been 

 regarded as HoloptycJm, but which almost all, in reality, belong to this new 

 species. This specimen likewise, I understand, originally formed a part of 

 the collection of Dr. Anderson. 



The specimen measures about twelve and a half inches in length, while its 

 depth nowhere exceeds two and a half inches. It is difficult to define the 

 posterior boundary of the head, but it appears to be about two inches long, 

 and its anterior contour slopes rapidly downwards to the sharp snout. 



The boundaries of the cranial bones are not traceable. Their surfaces 

 are almost smooth, and wholly devoid of such sculpture as is exhibited by the 

 bones of the head in specimens of HolojHycMus, in the same slab of sandstone. 



The scales are exceedingly thin, and all that can be certainly made out of 

 their structure is, that they have a circular outline, and are marked only by 

 fine, close-set, radiating ridges. The lateral line takes a curved direction from 

 the occipital region downwards to the middleof the body, and then coursesalong 

 the middle line to the tail. Its scales exhibit a slight longitudinal elevation. 



The pectoral fins are not visible in this specimen, but in another, traces of 

 them remain, and they appear to have been similar to the ventrals. The 

 latter are very remarkable. In the specimen imder description that of the 

 right side only is visible. It is attached, seven inches behind the end of the 

 snout, by a base which is nearly half an inch bro£ftl, and it attains a length of 

 2f inches. The central part of the fin is formed by a solid tapering axis 

 covered with small scales like those on the body, and the fine fin-rays are 

 disposed symmetrically along the anterior and posterior margins of this 

 central axis. 



Ventral fins having the structure which has been described, were more or 

 less plainly discernible in several of the specimens of Phaneropleiiron in the 

 collection of the British Museum. 



The rays of the dorsal fin commence a little in front of the middle of the 

 back, and of the root of the ventral fin. They are at first very short, but 

 they gradually increase in length backwards, as the dorsal line of the body 

 falls away in the caudal region, so that the top of the fin remains throughout 

 nearly on the same level, and forms a line parallel with the longitudinal axis 

 of the fish. The most posterior part of the fin, which attains a height of 1^ 

 inch, is consequently the deepest. 



No separation can be traced between the dorsal fin and the dorsal lobe of 

 the caudal, as which, in all probability, the posterior part of the dorsal should 

 be regarded. 



The inferior lobe of the caudal measures close upon three inches in length, 

 and attains nearly the same depth posteriorly as the dorsal lobe, or posterior 

 end of the dorsal fin. 



