A. Smith Woodward — On the Genus Notidanus. 213 



nized their true affinities some years ago when identifying fossil 

 vertebrata in the Oxford Museum ; I am also indebted to the kind- 

 ness of Professor Prestwich for the opportunity of studying and 

 publishing a further notice of the original teeth. 



The specimens in question were obtained from the Oxford Clay of 

 St. Clement's, near Oxford, and as they cannot be safely identified 

 with any form at present known, I propose to apply to the most 

 satisfactory tooth (Fig. 8) the provisional name of N. Daviesii : the 

 second fossil (Fig. 9) may possibly be a variety of the same species, 

 but this is at present uncertain. In the type specimen shown in 

 Fig. 8, the principal cone is relatively large, both in breadth and 

 height, and is destitute of serrations on its anterior border. This is 

 followed by four rapidly diminishing secondary cones, and the crown 

 terminates in a minute denticulation. The apices and edges of all 

 the cones are remarkably sharp, and the base is short and thick com- 

 pared with that of the majority of later species. The secoud tooth 

 (Fig. 9) has a very peculiar form, and consists merely of two back- 

 wardly curved cusps, though other small ones may have been broken 

 away behind. The lower part of the anterior edge of the principal 

 cone is crimped, and the enamelled sides of the crown exhibit vertical 

 wrinkles suggestive of those of Hybodus. 



N. Daviesii appears to approach N. Miinsteri more closely than any 

 other, but it is easily distinguished from this species by the different 

 relative proportions of the principal and secondary cones. 



9. N. microdon, Agassiz. PL VI. Figs. 10 — 15. 



1822. Tooth of Squalus? G. A. Mantell, "Fossils of South Downs," p. 227, 



pi. xxxii. fig. 22. 

 1843. JV. microdon, L. Agassiz, " Reeh. Poiss. Foss." vol. iii. p. 221, pi. 27, fig. 1 , 



pi. 36, figs. 1, 2. 

 1843? ,, ,, H. B. Geinitz, " Schichten und Petrefakt. d. sachsisch.-bohm. 



Kreidegeb." p. 38, pi. ix. fig. 2. 

 1846. ,, ,, A. E. Reuss, " Verstein. d. bohm. Kreideform." pt. ii. p. 98, 



pi. xlii. fig. 8. 

 1850. ,, ,, F. Dixon, " Geol. and Foss. Sussex," pi. xxx. fig. 30. 



1878. ,, ,, A. Fritsch, " Eept. u. Fische d. bohm. Kreideformation," p. 



12 (woodcut). 



Almost all the teeth of Notidanus met with in the Upper Cretaceous 

 formations are referable to a single widely-spread species, N. 

 microdon. This is a small form with a total number of five to nine 

 distinct cones in its side teeth, each of these being slender and sharply 

 pointed, and the principal cone usually much elongated compared 

 with the remainder : there are also well-marked denticulations on 

 the front edge of the crown. 



On examining a large series of specimens, such as that available 

 for study in the British Museum, considerable variations are at once 

 apparent ; but there are scarcely any discrepancies in size, and the 

 presence of intermediate forms renders it quite impossible to recog- 

 nize more than a single specific type. Some (Fig. 10) are obviously 

 from the front of the upper jaw, and consist only of a single large 

 cone, with one or two small denticles behind; while the short teeth, 

 with prominent principal cone and 4 — 5 secondary cones (e.g. Figs. 



