1868.] EGERTON LIASSIC FISHES. t)03 



has worked out the details of the cranial osteology in the other 

 genera of the Crolacanths, and as he has undertaken to follow up 

 that inquiry by a minute description of the specimen now under 

 consideration, in a future Decade, I shall only remark that the con- 

 tour of the head is remarkably similar to that of Macropoma in 

 the declivity of the frontal line and the general form of the com- 

 ponent bones, and that this specimen, taken as a whole, substan- 

 tiates entirely the truth of Professor Huxley's demonstration of the 

 remarkable persistence of type prevailing in this particular family 

 through the vast periods of geological time which must have elapsed 

 between the deposition of the lower beds of the Coal-measures and 

 that of the Chalk formation; and that I entirely agree with him in the 

 restricted view he takes of the Coelacanth family, by excluding 

 many of the genera assigned to it by Professor Agassiz. 



EuLEPiDOTUs SAUEOIDES, spcc. nov., Egcrtou. 



When Professor Agassiz first propounded his new classification of 

 fishes, the fossil forms then known were quite insignificant in number 

 compared with the voluminous lists we now possess. It is therefore 

 not surprising that the progress of discovery, by disclosing new forms, 

 should have rendered it imperative upon subsequent observers to 

 suggest some modifications of the original scheme, especially with 

 reference to the Ganoid order, with a view to arrange systematically 

 these new materials. The subject of the present description raises 

 the question of the validity of the distinctions between the Lepidoid 

 and the Sauroid families of the Ganoid order, as proposed by 

 Agassiz. The genera Lepidotus and Eugnathus may be selected as 

 fair types of the two families. The former is a massive fish, with a 

 thick head and blunt muzzle, in form very much resembling a Carp 

 of the present day ; the teeth vary from the crushing type (resem- 

 bling those of the Pycnodonts) to a more elongated conical form. The 

 body is covered with thick rhomboidal scales of large and tolerably 

 uniform size on the flanks and belly ; the fins are of moderate 

 dimensions, not calculated for swift progression, and the tail is 

 homocercal. The latter, on the contrary, is a slender fish, tapering 

 gradually from head to tail ; the teeth are of two sizes, as in 

 Lepidosteus of the present day, the long and sharp prehensile teeth 

 being intermixed with small needle-shaped teeth, for retaining the 

 slippery prey ; the dorsal fin is not far back, and the semiheterocercal 

 tail is an organ of great power ; the scales are small compared with 

 the size of the fish, and vary much in shape and size in the different 

 parts of the body ; in particular on the ventral region, and espe- 

 cially around the insertions of the fins, the scales become as much 

 elongated as the scales of Ptycholepis. In every respect, therefore, 

 this is a fish of prey, having all its organization specially adapted for 

 a predatory life, as the former may be considered adapted for 

 sluggish habits and a testaceous or, may be, herbaceous diet. The 

 subject of this notice occupies an intermediate station between these 

 two forms. The body is more elongated than in any Lepidotus — as 

 much so, in fact, as in Eugnathus Plulpot'KB. The head, although 



