402 On some British Upper Jurassic Fish-remains. 



hitherto been recorded from the Upper Jurassic of Engdand, 

 one from the (Jxford Chiy of Yorkshire * and two others 

 from the same formation near Oxford f. It is thus interesting 

 to note that a fourth specimen has been discovered more 

 recently bj Mr. Thomas Jesson, F.G.S., in the Oxford Clay 

 of St. Ives. This is a well-preserved tooth, shown of the 

 natural size in fig. 5, and considerably differing from each of 

 the others. 



The new fossil has a shallow and somewhat crimped root ; 

 and the crown consists of a very large principal cone, followed 

 by three secondary cones decreasing in size, with a minute 

 posterior denticle. The enamel is quite smooth, and the 

 gracefully sinuous anterior margin of the principal cone 

 exhibits only the feeblest crimping, no denticulation. 



The specific determination of the isolated teeth of Selachian 

 fishes is, of course, nearly always a matter of speculation ; 

 but it is convenient to have names for purposes of quotation. 

 As the new tooth, therefore, does not appear to differ in any 

 essential respect from some of the specimens found in the 

 Oxfordian, Corallian, and Lower Kiinmeridgian of the Con- 

 tinent, commonly referred to Notidanus Muensteri, it seems 

 advisable to provisionally record this specimen under the same 

 name. 



Form, and Loc. Oxfordian ; St. Ives, Huntingdonshire. 



EXPLANATION OF PLATE XVIII. 



Fi(j. 1. Caturus an(jiiMus, Agassi z ; fisli wanting head, lateral aspect, one 

 half nat. size. — Portlandian ; Garsington Hill, Oxford. [Wor- 

 cester Museum.] 



Fig. 2. Gyrodus ptmctatus, Agassiz ; portion of vomerine dentition. — 

 Corallian (Lower Calcareous Grit) ; Browse Pit, Malton, 

 Yorkshire. [Malton Museum.] 



Fig. 3. Ditto; left splenial dentition. — Corallian (Lower Calcareous Grit) ; 

 Malton. [Malton Museum.] 



Fig. 4. Ditto ; large right splenial dentition, apparently crushed. — 

 Corallian (Lower Calcareous Grit) ; Browse Pit, Malton. 

 [Malton Museum.] 



Fig. 5. Notidanus Muensteri, Agassiz ; tooth, outer aspect. — Oxfordian ; 

 St. Ives. [British Museum, no. P. 67.34.] 



[Figs. 2-5 are of the natural size.] 



* Notidanus serratus, Fraas, Smith Woodward, Geol. Mag. [3] vol. iii. 

 (1886), p. 212, pi. vi. tig. 7. 



t Notidanus JJaviesi, Smith Woodward, ibid. p. 212, pi. vi. figs. 8, 9. 



