436 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jlino 18, 



highly probable, they possessed lobes. The fins are rayed, and 

 the rays appear to have subdivided as they approached their extre- 

 mities : they are very large. The head is rather small in proportion 

 to the size of the fish, short and depressed. The cranial bones appear 

 to have been sculptured, but are very imperfectly preserved; two 

 large parietals, placed in close juxtaposition, but distinct, are the only 

 tolerably entire portions of the skull. There are also the remains 

 of what look like three occipital plates, and also of what I suppose 

 to have been a supratemporal bone, of considerable size. The under 

 side of the head is not shown. The scales are cycloid in form, and 

 in this specimen nearly half an inch in diameter ; they were thick 

 and strong, although less so than those of HoloptycJiius. The general 

 character of the markings on the scales shows very minute, granular, 

 radiating striae, — the granular markings being so arranged as to have 

 the appearance of concentric circles. This marking, however, appears 

 to have been occasioned by the internal structure of the scales. In a 

 few the external sculpturing is partially preserved ; these seem to 

 have all the characteristic sculpturing of the scales of Glyptolepis, 

 their surface being divided into two nearly equal portions, the one 

 covered with small tubercles in lines radiating towards, but not 

 reaching, the centre, the other having distinctly marked ridges, be- 

 coming rather fainter towards the edge of the scale. Extending 

 beyond, and in the same line as that in which the posterior portion 

 of the body of this fish lies, are a great number of scales, of the same 

 character as those covering its body, as if, when first laid down, the 

 creature had been extended at full length, but before being finally 

 entombed it had been folded over, leaving a large number of de- 

 tached scales on the sand where it first lay, and these had been 

 afterwards covered up and preserved. 



On the same slab the impression of another fish, about 9 inches 

 in length, is also preserved. This, although very imperfect, seems, 

 from the character of its scales, .&c., to have belonged to the same 

 genus ; while, on carefully examining other slabs, many scales, some- 

 times singly, sometimes in masses, and having the same characteristic 

 markings well preserved, are by no riaeans uncommon. 



The general features of this fossil seem to ally it so closely to 

 Olyptolepis, that I have little doubt that it will be found to be- 

 long to that genus; but in several features it diverges considerably 

 from any of the species I have yet seen : the scales, although 

 similarly ornamented, have the sculpturing larger and more promi- 

 nent, the fins are more fully developed, and while the caudal fin in 

 the others is described as heterocercal, in this the upper and lower 

 lobes are very nearly equal. 



Conclusion. — The Dura Den sandstones have thus, up to the pre- 

 sent time, yielded six well-marked genera, viz. Holoptychius, Gly- 

 jotolcemus, Phanerojpleuron, Pterichthys, Gflyptopomus, and Glyptolepis. 

 Each of these genera seems there to be represented only by one species, 

 with the exception of Holoptychius, and even in this genus the ex- 

 istence of more than one species is doubtful. Nowhere else, all 



