NEWTOX : OPALIZED SHELLS OF NEW SOUTH WALES. 233 



Remarks. — Mr. Etlieridge, jun., has carefully studied the merits of 

 Moore's imperfectly defined species, Natica variabilis and Delphinula 

 rejlecta, and has acknowledged the difficulty of separating them on 

 account of the similarity of their characters. He has alluded to the 

 presence of an ovate aperture in the first- named, and one of rounder 

 contour in tlie otlier, as of some importance, although an unfortunate 

 slip in the text informs lis that it is " ovate " in both. Apart from 

 this, however, Mr. Etheridge's figures do not assist us as to the actual 

 roundness of the aperture in the species rejlecta, in whicli case it is 

 thought that tlie apertures for both would be better diagnosed as 

 more or less ovate, and consecjuently both species might with 

 advantage be united, more especially as the romaining characters are 

 very similar in each ; it is, therefore, suggested to retain variabilis. 



Well-preserved specimens are seen to be ornamented with fairly 

 strong growth-lines, crossed by microscopically small, close, and spiral 

 striations ; one specimen, liowever, in the Britisii Museum (Mineral 

 Dept.) exhibits a series of thick, equidistant, vertical costae on the 

 penultimate whorl, which is a somewliat unusual structure, having a 

 resemblance to what is occasionally seen on the spire of Gyrodes pansus 

 from the Indian Cretaceous as figured bj- StoHczka,' who regarded such 

 markings as raised striae of growth, while Mr. Etlieridge, jun., has 

 noted and figured the same ornament in an example of the species 

 from the Lower Cretaceous deposits of South Australia, which, like 

 the present specimen, has the general characters of Natica variabilis 

 (see pi. vi, fig. 17, Mem. Koy. Soc. S. Australia). 



Another difficulty presents itself as to the pioper genus with which 

 to associate this species. Mr. Etlieridge, jun., recognized it as 

 belonging to Fischer's Pseudamattra, of which the tvpe is Natica 

 bidblformis of J. de C. Sowerbyfrom the Austrian (Gosau) Cretaceous; 

 but that seems an unsatisfactory determination, because the Austrian 

 fossil has a much more elongate and tabulate spire, as well as 

 possessing an extensive callus to the inner lip, and is besides without 

 any indication of an umbilical opening. The Australian shell much 

 more nearly approximates in spiral structure to the Cretaceous 

 Gyrodes, although removed from it by the absence of a wide basal 

 excavation whicli characterizes that genus. It is now suggested 

 that Agassiz's Euspira^ sliould include this species, which was 

 founded on Natica glaucinoides of J. Sowerby from British Lower 

 Eocene rocks, and which seems to embrace, in a more or less modified 

 manner, the chief characters of the shell in question. 



Locality. — White Cliffs, jS'ew South Wales. 



Collections. — British Museum (Geol. Dept., G. 19602-3 ; Mineral 

 Dept., -AVr- , -1^9-0-^-) ; Bev. F. St. J. Thackeray. 



Distribution. — Lower Cretaceous: South Australia; Queensland. 

 Upper Cretaceous : White Cliffs, New South Wales. 



^ "Cretaceous Fauna of Southern India (Gastropoda) " : Mem. Geol. Surv. 



India, Palseontologia Indica, vol. ii, pi. xxii, fig. 9a, 1868. 

 - Desor & Agassiz, Conchyliologie Minei-alogique de la Grande Bretagne par 



James Sowerby, traduit de I'Anglais, p. 1-5, 1838. 



