g o CLADOSELACHIAN SHARKS 



and the writer now finds that an exceedingly simple con- 

 dition existed in the neural and haemal arches ; they prove 

 to be of moderate size and thickness, each a tapering rod 

 of cartilage, forked at its base ; each body segment con- 

 tains a single neural and haemal spine, closely alike in size. 

 Unlike modern sharks, Cladoselache was without claspers : 

 its eggs must have been fertilized after their deposition, as in 

 the majority of fishes other than Elasmosbranchs. The gill 

 openings, at least seven (probably nine) in number, appear 

 as in the restoration, to have been shielded anteriorly by 

 a dilated dermal flap. A spiracle was probably present. 

 The jaws were slender, and apparently hyostylic (p. 257) ; * 

 the teeth are of the pattern of shagreen denticles, but occur 



Fig. 86 B. Teeth of (" Cladodus") Cladoselache. X . The above forms 

 occur in different regions of the mouth. 



in clusters (^Cladodus" Fig. 86, B). The mouth was ter- . 

 minal in its position. The nasal capsule was apparently 

 not connected with the mouth by a dermal flap. The eye 

 was protected by several rings of rectangular plates, clearly 

 shagreen-like in character. The integument was finely 

 studded with minute lozenge-shaped denticles, and was 

 everywhere lacking in membrane bones. The lateral line 

 retained its groove-like character. 



The shark, Acanthodes (Fig. 87), of the Coal Measures 

 is now to be regarded (Smith Woodward) as a member of 

 a highly specialized Palaeozoic group. And its many spe- 

 cialized structures added to its greatly reduced size 



* As Claypole's recent figure seems to demonstrate. Am. Geol.^Jan. 



