114. 



according to Zittel it is allied to tlie Mediterranean P. poly- 

 moj'phus, Br., but I have no specimens of that species for com- 

 parison. 



Sturt has given a very good figure of a small example of this 

 species, identifying it with the European P. coarctatus ; Teni- 

 son- Woods reproduces Start's figure on p. 76 of his " Geol. 

 Observations," and in his "Introduction to the Tertiary Rocks 

 of South Australia," Phil. Soc, Adelaide, May, 1865, refers 

 Sturt's shell to P. Gamhierensis. From this association I 

 dissent, as Sturt's figure well shows the umbonal corrugation 

 and inflexed front so characteristic of P. ince^'tus, and more- 

 over P. Gamhierensis does not occur in the Murray cliffs, 

 whilst P. incertus is not a rare shell. 



Pecten Hochstetteri, Zittel. 



Reference. — P.Hochstetterri,Zi^«feZ,in Palseontologievon Neu- 

 Seeland, p. 50, t. xi., figs. 6a and 5c? (non 5b), 1864 ; and Hutton 

 in Cat. Tertiary Possils of New Zealand, p. 30, 1873. 



Synonym. — Pecten pleuronectes, Tenison- Woods, in Proc. 

 Phil. Soc, Adelaide, 1865, pi. i., fig. 5 (non Gmelin). 



Shell nearly orbicular, equivalve, equilateral, thin, com- 

 pressed ; both valves smooth, but when slightly weathered 

 showing fine concentric striae. Ears of right valve subequal, 

 roundly truncated, transversely striated, the anterior one 

 slightly sinuatedly striated. Ears of left valve equal, obliquely 

 truncated, transversely striated. Interior of valves without 

 ribs. 



Dimensions. — Longitudinal diameter 58, transverse diameter 

 60 millimetres. 



Localities. — White coralline limestone at Mount G-ambier ; 

 Taggy limestones at Mannum, Eiver Murray ; the glauconite 

 limestone, Aldinga Bay ; glauconite clayey sands, Adelaide 

 bore ; yellow clayey sands, Moolowurtie, Yorke Peninsula ; 

 Oamaru formation of New Zealand from several localities. 



Having specimens of P. Hochstetteri from New Zealand, I 

 can with certainty announce the fact of this species occurring 

 in the Older Tertiary rocks of South Australia. 



Zittel describes the right valve as radially ribbed, which is 

 represented by his fig. 56 ; but specimens agreeing with his fig. 

 5« have been obtained with the valves in opposition, both of 

 which are smooth. Hutton amends Zittel's diagnosis, exclud- 

 ing fig. 56, which belongs to another species, apparently 

 P. Yahlensis, Tenison-Woods. 



P. Hochstetteri has an external resemblance to the species 

 of the Pleuronectes group, but it is devoid of internal ribs, 

 and is equivalve. This type is w^ell represented in the Euro- 

 pean Jurassic rocks, indeed our species verv much resembles 



