3 
IT -DESCrilPTlON OF THE GENERA AND SPECIES. 
Class — Pisces. 
SELACHII. 
CESTRACIONTID^. 
Genus non del. 
Ohs . — An imperfect fossil, 0‘33 in length, indicates the presence of 
a Selachian in the Ilawkcsbnry beds, hut does not exhibit snlheiently 
characteristic features for its generic determination. Each of the tAvo 
dorsal fins of the fish is armed AAdth a formidal)le spine ; and the body is 
evidently covered with dense shagreen. The first dorsal fin-spine is much 
arched and sharply pointed, measuring 0'06 in length, and about O'OOS in 
breadth at the base; and there are some faint appearances of tubercles, 
suggesting a surface-ornament of longitudinal nodose ribs. The second 
dorsal spine is placed OA75 behind the first, hnt only the base is preserved. 
The shagreen-granules are deeper than broad ; and these seem to have been 
transversely ribbed or pectinated. 
The discovery of satisfactory specimens of this Shark aaoII prove of 
much interest, for the fcAV features discernible — especially the characters of 
the shagreen — are very suggestive of a British Carboniferous Selachian, 
Sphenacantlms.^ Teeth indistinguishable from the late Pahcozoic DipJodus 
occur in the English KenjAcrf ; the dorsal fin-spine, Ncniacanthus, of the 
llhoetic has the posterior denticles laterally placed, as in all Palaeozoic 
spines ; and the lllnctic teeth, named Ihjhodus minor, have the base so much 
horizontally exjAanded that they Avould bo assigned to Cladodus if found in 
the Carboniferous. But no undoubted proof of a Palaeozoic Selachian genus 
* L. Agassiz, Recherclies sur les Poissons Fossiles, 1837, A"ol. iii, p. 23. Provisionally defined in the 
Catalogue of the Fossil Fishes in the British Museum, 1889, Part 1, p. 241. 
+ Smith Woodward, “On Diplodiut Moorei, sp. nov., from the Keuper of Somersetshire,” Ann. Mag. Nat. 
Hist., 1889 [0], Vol. iii, pp. 299, 300, PI. xiv, figs. 4, 5. 
lift 74—90 D 
