182 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



Aecopeena eecens, n.sp. 



Shell thin, translucent, vitreous ; obliquely oval, much inflated ; 

 rounded at the extremities, much more dilated behind than in front. 

 ITmbones very large, obliquely inclined forwards, cordiform and sub- 

 marginal. Posterior hinge-line arched, six millimetres long, with 

 a well-defined subintei'ual ligamental groove ; anterior hinge-line 

 nearly straight, about one-third the length of the posterior part. 



Exterior surface ornamented with concentric folds and intervening 

 striae, and by radial costules ; the intercrossing of the two sets of 



Arroperiia rcceiis, n.sp. 



threads producing a fine recticulate ornament. The radial costules are 

 subacute, serrated by the concentric striae, and are a little wider than 

 the intervening sulci ; in the medial part of the ventral margin there 

 are five costules to each millimetre of width ; the costules sharply 

 serrate the margin. 



The adductor impressions are indicated by greater translucency of 

 the test ; the posterior one is large and rounded ; the anterior one is 

 smaller, but conspicuous, narrow-oblong, and situated close under the 

 anterior margin of the hinge-line. 



Dimensions.— Transverse diameter of closed valves, 1 5 mm. ; nmbo- 

 post-ventral diameter, 19 mm.; antero-posterior diameter, l7mm. ; 

 umbo-ventral diameter, 14 mm. 



Locality. — Port Esperance, Tasmania ; two perfect shells (one with 

 contained animal) and a single valve dredged by Mrs. Harrison. My 

 collection and that of Mrs. May. 



Ajfinitins. — In point of size the recent species approximates to 

 A. filosa, but that shell, judging from Conrad's figure of it, has more 

 projecting umboues and a different outline. A. recens finds a near 

 relation in A. radiolata, Deshayes, but it differs in shape and in its 

 finer ornamentation. 



