500 PROCEEDIN^GS OE THE GEOLOOICAL SOCIETY. [Jline 17, 



year has passed without some revelation of Liassic times having 

 been elicited by the assiduity of the collectors in that far-famed 

 locality. Of fish alone we now reckon thirty- one distinct genera, 

 comprising seventy-nine species ; and of the latter not more than two 

 or three have been clearly identified as occurring elsewhere. The 

 following is a short description of some of the novelties which have 

 occurred in the last year or two. As the specimens are large and 

 worthy of full pictorial illustration, the more detailed account will 

 be reserved foi- one of the forthcoming Decades of the Memoirs of 

 the Geological Survey. 



OSTEOKACHIS MACROCEPHALTJS, gCU. ct SpCC. UOV., EgOrtOU. 



The description of this new genus is taken from three specimens 

 in the collection of the Earl of Enniskillen. The most remarkable 

 features in them are the massive dimensions, and complete ossifica- 

 tion, of the bodies of the vertebrae ; and these have suggested the generic 

 appellation. They all appear to belong to one species, characterized 

 by the large size of the head and the multiplicity of the teeth. It is 

 quite possible that a small fragment of a jaw in the same collection, 

 named by Professor Agassiz Eugnatlnis polyodon, may have belonged 

 to this species, in which case (if proved) the specific name I have 

 adopted will have to be replaced by "polyodon.''^ The fish when 

 entire must have been two feet or more in length ; the head mea- 

 sures 7 inches. The deepest part of the body was at the shoulder- 

 girdle, from which point the outlines gradually converge, until at the 

 ventral fins the depth is 3| inches. The bones of the head are 

 largely developed, especially the epitympanic and hypotympanic or 

 quadrate bone. The latter has a strong articulating condyle for the 

 attachment of the lower jaw. AH the bones in the oral cavity are 

 densely beset with small sharp teeth, associated, on the maxillary, 

 premaxiLlary, and mandibular bones, with conical teeth of larger 

 dimensions. The surface of the head was roughly ornamented with 

 elevated blotches of enamel of vaiying form and size. The column 

 contained about forty vertebrae, measuring nearly half an inch each 

 in diameter; they are completely ossified. The neural processes 

 are proportionately strong, and are united to the centres by broad 

 bases. The pectoral fins are long and broad ; the component rays 

 are single for an inch and three quarters, but are bifurcate and cross- 

 jointed in the distal portion of the fin. The ventral fins are of 

 moderate dimensions, and contain about eight rays each ; they are 

 supported by strong pelvic bones. The dorsal fin is immediately 

 over the ventrals ; t he interspinous bones supporting it are long and 

 strong. There are no fulcral or marginal osselets discernible ; but 

 the main rays, to the number of a dozen, are preserved. The anal 

 fin is placed near the tail ; it contains seven or eight rays. The 

 caudal organ is not preserved in any of the specimens. The scales are 

 large and solid, firmly locked together by a pin-and-socket appara- 

 tus. The surface is beset with tubercles and granules of a lustrous 

 ganoine, coarser and more frequent on the scales covering the an- 

 terior and middle part of the trunk than on those nearer the tail. 



