58 NEW YORK STATE MUSEUM 



ever view we may adopt as the naming of the parts, these cartilages are as 

 much reduced as in a modern herring. Dr Dean speaks of the " radials " of 

 Cladoselache as if, by fusion, they might readily become a fin spine like 

 that of the Acanthodian Parexus ; but the former are cartilage and endo- 

 skeletal, the latter is merely the ordinary dentine and therefore presumably 

 exoskeletal. The problem of the primeval sharks continues to present 

 endless difficulties, but these are only multiplied by such comparisons. In 

 the present writer's opinion, the pectoral of Cladoselache is more remotely 

 connected with that of the Acanthodians than is that of a modern Siluroid 

 with the pectoral of the Devonic Holoptychius. Everything still tends to 

 show that the very highest Elasmobranchs lived simultaneously with almost 

 the lowest in late Paleozoic times ; while sharks and skates nowadays are 

 a comparatively degenerate race. 



Formation and locality. Naples shale (Portage beds) ; Eighteen Mile 

 creek, near Buffalo, N. Y. A tooth of an undetermined species of Cladodus 

 is also recorded by J. M. Clarke,' from the Chemung beds at High Point 

 (High Point sandstone), near Naples, N. Y. A mass of confused dermal 

 plates, or shagreen, with prominent denticulations and possibly referable 

 to Cladoselache has been obtained by Dr Clarke from the Marcellus shale 

 of Leroy, N. Y,, the original being preserved in the State Museum. 



Order ICHXHYOTONII 

 This order is represented in the Devonic only by detached teeth 

 similar to those occurring in well known Pleuracanthid genera, and consist- 

 ing of two or more sharp cusps attached to broad bases. No satisfactorily 

 [:»reserved remains, other than teeth, are known from an earlier period 

 than the Lower Carbonic, and the most complete are of Permian age. It 

 is customary to refer to this order most of the detached teeth known as 

 Cladodus, although it is certain that teeth of the same form were common 

 to several primitive genera — perhaps even to more than one family and 



order. 



Family f»lp;uracanthidae 



(lenus DiPLonus 



Under this name are comprised a number of Paleozoic species known 



only by the evidence of detached teeth, hence the status of the genus is 



■U. S. Geol Siir. Bui. 16. 1885. p. 72. 



