ON THE EXCAVATIONS IN DURA DEN. 33 



or their outer surfaces. The operculum is a broad bone, larger behind, 

 where it is convex, than in front, where it is concave, and much longer than 

 it is deep. 



" The rami of the lower jaw are stout and strong, and form a very broad, 

 almost semicircular arch. The characters of the scales are well known. 

 The fins are lobate, and the dorsal fin is small and triangular. Sir Philip 

 Egerton, in a valuable memoir recently read before the Geological Society, 

 expresses his belief that Holoptychius has two dorsal fins. I am very loath 

 to controvert the opinion of so experienced and skilful an observer, the more 

 particularly as specimens of Holoptychius with perfect tails are very rare, 

 but one or two complete examples I have seen, leave no room in my mind 

 for any other conclusion than that stated above." 



Numerous perfect specimens of this remarkable fish have been obtained 

 in our recent excavations, which show the lobate character of the fins as de- 

 scribed by the learned Professor, as well as the unity of the dorsal organ. 

 The entire form of the body of Holoptychius is likewise beautifully deve- 

 loped in some of the specimens, where the caudal end appears gradually 

 tapering to a point, and not at all bent up as represented in all former de- 

 scriptions ; while the ventral lobe of the caudal fin, though rather shorter than 

 the dorsal lobe, has nearly the same depth, and not in the ordinary sense 

 of the heterocercal structure. 



In the course of our explorations we also succeeded in obtaining several 

 perfect specimens of two new and hitherto undescribed genera of Ccelacanths, 

 namely, Glyptolcemus Kinnairdii and Phaneropleuron Andersoni. 



The specific distinction of Glyptolcemus Kinnairdii was proposed and 

 adopted at the Meeting of the London Geological Society in honour of 

 Lord Kinnaird, whose zeal in promoting the interests of geology is only 

 equalled by his enlightened endeavours to advance the interests of anything 

 connected with our social and industrial well-being as a statesman. The 

 generic term of Glyptolcemus was suggested on account of the marked 

 sculpture of the jugular plates in one of the specimens. As described in the 

 "Monograph" of Dura Den, the scales and fins likewise form strongly 

 marked characteristics of this new genus. 



The scales are rhomboidal, and have an average short diameter of one- 

 sixth of an inch. Twenty-four series are visible, and diverge from the me- 

 dian line in the ordinary way ; they are larger on the anterior part of the 

 ventral surface than on the posterior part, and at the side of the body than 

 on the belly. They are pitted and ridged almost as in Glyptopomus, although 

 somewhat thinner and less bony than in that fish. There are two dorsal fins 

 which are situated very far back, the anterior edge of the root of the first 

 being nine inches distant from the end of the snout in one of the specimens : it 

 is remarkably slender, and of a semi-oval outline. The second dorsal fin is 

 considerably larger than the first, being two inches on its longest axis, and 

 its breadth about an inch in depth. The entire length of the body, in several 

 of the specimens, varies from a foot and a half to nearly two feet. 



The other new genus discovered in the course of our explorations is the 

 Phaneropleuron Andersoni, and from some very imperfect fragments named 

 by Professor Agassiz as a Glypticus, but without describing or defining the 

 genus. The generic appellation, now bestowed by Professor Huxley, ex- 

 presses the most striking character of the fish — the curious development and 

 obtrusiveness of its ribs, arising from their complete ossification as well as 

 the thinness of the scales. The affinity of Phaneropleuron with the typical 

 ccelacanths is indicated not only by its singular tail, but by its persistent 

 notochord, by its lobate pectoral and ventral fins, and by its well-ossified 



1860. d 



