90 Reports and Proceedings — 



standing of " wemmelensis" as useful among Nummulites; but " Prest- 

 wichiana " has to give way to " elegans " for the peculiar " Barton " 

 variety. A bibliographical history of the long-misunderstood N. 

 elegans, Sowerby, description of this form and of iV^ variolaria (Lam.), 

 notes on N. Icemgata (Brug.), and an account of their range in 

 England, complete the paper. 



2. " On the Dentition and Affinities of the Selachian Genus 

 Ptychodus, Agassiz." By A, Smith Woodward, Esq., E.G.S. 



The genus Ptychodus, owing to the detached condition in which 

 the teeth are usually found, has hitherto been imperfectly under- 

 stood. Agassiz referred it to the Cestraciontidee on account of a 

 supposed resemblance in the arrangement of the teeth, and Owen's 

 researches on their microscopic structure served to confirm this view. 

 On the other hand, several writers have pointed out characters 

 tending to show affinity between PtycJiodiis and Bhynchobatus. 



More recently, however, Prof. Cope and the author had shown 

 that the supposed affinities between Ptychodus and the Cestraciontidse 

 were only apparent, and in the present paper additional evidence 

 was brought forward. 



The author proceeded to describe several specimens of P. decur-^ 

 rens in the British Museum, and in the collection of Mr. H. Willett, 

 of Brighton, one of the latter, especially, containing, what had been 

 previously entirely unknown, the dentition in part of both jaws.. 

 These specimens showed that each jaw contained six or seven longi- 

 tudinal rows of teeth on each side of the median row, and that the 

 genus must be referred to the true Eays, and not to the Cestraciont 

 Sharks, though the precise family to which Ptychodus belongs was 

 more difficult to determine. On the whole, the writer was disposed 

 to assign it a place either amongst the Myliobatid^ or in their 

 neighbourhood. The microscopic structure of the teeth was shown 

 to be insufficient, by itself, to show their affinities. 



3. " On a Molar of a Pliocene type of Equus from Nubia." By E. 

 Lydekker, Esq., B.A., F.G.S. 



A small collection of Mammalian remains from near Wadi Haifa 

 had recently been placed in the author's hands ; some of the bones 

 were mineralized similarly to those of the Upper Pliocence of the 

 Val d'Arno, or the Lower Pleistocene of the Narbadda valley. 

 Amongst others the most interesting is a right upper cheek-tooth 

 of Equus but little worn. It evidently does not belong to any of 

 the late Pleistocene or Eecent species of the genus, but to the more 

 generalized group comprising E. sivalensis, etc. : though, bearing 

 in mind the impossibility of distinguishing many of the existing 

 species of the genus by their teeth alone, its absolute specific identity 

 is not asserted. We may infer, then, that the ossiferous beds of 

 Wadi Haifa are not improbably of Pliocene age, since this group 

 of Horses, both in Europe, Algeria, and India, had totally dis- 

 appeared after the period of the Forest-bed. Moreover, it is of 

 interest, in view of previously expressed opinion, to find in the Ter- 

 tiary of Nubia a species of this primitive group of Equus which is 

 apparently more nearly allied to the Siwalik than to the European 

 species. 



