CAPISTROCAKDIA. 383 



and there are corresponding differences in the disposition of the 

 concentric lineations, which in C. pyxidata are somewhat smaller. 

 The author compares it with the young of C. ephamilla, from 

 which it may be distinguished in being less inequivalv^e, more 

 convex, with larger umbones, and proportionately shorter. Keel 

 on the surface of the shell conspicuous ; radial strice very minute. 



Dimensions. — Height 7 mm. ; length 10 mm. 



Form, and Loc. — Eocene : Aldinga, South Australia. 



L. 9898. Examples of the neanic and ephebic stages of 

 growth. Purchased. 



Family SAXICAVID^. 

 Genus CAPISTROCARDIA, Tate. 

 [Trans. Eoy. Soc. South Aust. vol. ix. 1887, p. 179.] 



The shell in this genus has the dentition of Ghjcymeris {Panopcea, 

 and.), with an external resemblance to Saxicava ; but it differs 

 from both of those genera by having closed valves ; it has an um- 

 bonal rib confluent with the cardinal tooth, extending vertically 

 across the interior to near the ventral margin ; pallia! line broken 

 up, and there is, apparently, no sinus. 



Type. — Capistrocardia fray His, Tate. 



Capistrocardia fragilis, Tate. 



1887. Capisfrocardia fragilis, Tate, Trans. Eoy. Soc. South Aust. vol. is. 

 p. 180, pi. xix. fij,'s. Ua-b. 



" Shell small, thin, translucent, traversely elongate-oblong. Um- 

 bones depressed, approximate, near to the anterior margin. Anterior 

 margin rounded ; dorsal margin sloping backwards, forming an 

 obtuse angle with the posterior margin, which is straight or slightly 

 convex outwardly ; ventral margin straight, save for a broadish 

 post-medial inflexion. The umbonal ridge, extending to the 

 post-ventral margin, is moderately raised and roundly angulate. 

 The exterior surface of the valves is smooth and concentrically 

 distantly striate; a few lamellae appear towards the margins." — Tale. 

 The figures given by the author are not of much service, but the 

 following specimens agree with the description above quoted. 



