90 Proceedings of the Royal Society of Victoria. 



Dall says of P. perlata, Conrad, that it is an ilLdetitied species, 

 and apparently scarcely recognisable.^ Bouvier and Fischer in 

 the monograph referred to also refer P. gigas, Borson, and 

 P. atlantica, Cotter, both to the recent section Entemnotrochus, 

 and are inclined to the opinion that tliese two species are 

 identical. 



Concerning P. sismondai, Goldfuss, Crosse and Fischer state- 

 that the exact locality of the shell appears doubtful, it is given 

 as the Upper Mai-ine Sands of the neighbourhood of Bunde. 



In the description of P. bianconii, d'Archiac, the author 

 queries his generic location of this species in the text, but not on 

 his plate. 



P. duboisii, Mayer, was first described as Trochus giganteus. 

 Dubois, and as that specific name was preoccupied, it was named 

 after Dubois by Mayer. 



P. whittieldi, Vincent, has also been treated in a similar way 

 by Vincent, for- this species was first described as P. gigantea, 

 Whitfield ; this name, as in the previous case, being preoccupied 

 by Sowerby for a Lower Greensand fossil, a change was 

 necessary. 



Our total information then on these Tertiary species appears 

 to be of a somewhat meagre order, and if it is accepted that one 

 of the American species is not recognisable, that P atlantica and 

 P. gigas are identical, and that P. fischeri is only a MS. name, 

 our total number dwindles to sixteen, and the amount of readily- 

 available informacion on several of these is so slight, that 

 further details concerning them and their occurrence would be 

 very acceptable. 



Of forms older than Tertiary, about twelve hundred species 

 are known, and these are about equally divided between the 

 Palaeozoic and Mesozoic, but the Jurassic undoubtedly holds the 

 maximum with about four hundred species. 



I wish to express my thanks to Professor W. Baldwin Spencer, 

 Director of the National Museum, for allowing me to refigure 

 the type of P. tertiaria, and to Mr. F. Chapman for kindly 

 photographing it. 



1 Ti-ans. Wag. Inst., Philad., vol. iii., pt. 2, p. 423, 1892. 



2 Jour. d. Conch., vol. ix., p. 162, 1861. 



