BRITISH FOSSILS, 



Decade X. Plate III. 



PHANEROPLEURON ANDERSONI. 



[Genus PHANEROPLEURON. Huxley. (Sub-kingdom Vertebrata. Class Pisces. 

 Order Gauoidei. Sub-order Crossopterygida). Family Phaneropleurini.) Body elon- 

 gated, tapering to an acute point posteriorly, compressed from side to side. Dorsal fin 

 single, extending for nearly the length of the posterior half of the body ; the paired fins 

 acutely lobate ; the ventrals very long, apparently longer than the pectorals, and situated 

 beneath the anterior end of the dorsal fin. Tail inaiquilobate, the upper lobe being by far 

 the smaller. Scales cycloid, very thin. Teeth numerous and conical; Neural arches, 

 ribs, and interspinous bones well ossified.] 



Phaneropleuron Andersoni. Sp. Unica. 



All the specimens of tliis species and genus at present known 

 have been procured from the Old Red Sandstone at Dura Den, 

 associated with IloloptycJiiuSj the two genera being constantly 

 found associated in the same slabs of sandstone. A fine series of 

 examples is to be seen in the British Museum and the Museum of 

 Practical Geology, the whole of which, I believe, were collected by 

 Dr. Anderson, in whose work upon Dura Den the first description 

 of the present species appeared. The fish had received the name 

 of Glypticus from Agassiz long before, but the name was unac- 

 companied by any description or definition, and has been used 

 for a genus of Echinodermata. The most complete specimen 

 I have seen is that figured (two-thirds of the natural size) in 

 Plate III. fig, 1, which occurs among a number of other examples of 

 this genus and of Holoptychius, in a fine slab marked 26120 in the 

 collection of the British Museum. 



The length of body equals about 5^ lengths of the head. It remains 

 of tolerably equal thickness from the pectoral region to that of the 

 ventral fins, and then gradually tapers off to a finely pointed caudal 

 extremity, which is, usually, slightly bent upwards. When the 

 mouth is shut, the head also presents a triangular contour, both its 

 upper and its under outlines rapidly shelving towards the snout. 



The scales are exceedingly thin, and, apparently in consequence of 

 containing very little bony matter, they are apt to run into one 



[X.] * 10 D 



