908 MR. G. F. ANGAS ON NEW AUSTRALIAN MOLLUSCA. [NoV. 28, 



5. On a New Genus and some New Species of Marine Mol- 

 lusca from Port Jackson^ New South Wales. By George 

 French Angas, F.L.S., C.M.Z.S. &c. 



(Plate XLIV.) 



Genus Alicia, Arigas. 



Shell inequivalve, transversely ovate, thin, slightly compressed, 

 not gaping ; beaks entire, interior subnacreous. Hinge composed 

 of a posterior more or less prominent callus in the right valve, fitting 

 into a corresponding depression in the left valve, and an anterior 

 elongated marginal lamellar tooth or ridge ; cartilage internal, situ- 

 ated perpendicularly under the umbones, and covered by a large tri- 

 angular ossicle. Muscular impressions moderate ; pallial Hue si- 

 nuated. 



This genus has much the appearance externally of Periploma, but 

 the ossicle is large and triangular as in Lyonsia. It differs from both 

 genera in the cartilage not being supported by projecting spoon- 

 shaped processes, and in its being perpendicular to the umbones. 



Alicia angustata, n. s. (PI. XLIV. fig. 1.) 



Shell elongately oblong, white, surface of valves (under the lens) 

 very finely decussated, inequilateral ; anterior side five-sixths the 

 length of the shell, rounded at the extremity, the dorsal margin 

 slightly convex ; posterior side truncate at the extremity, the dorsal 

 margin incurved, umbonal slope angulated ; ventral margin almost 

 straight. The hinge with the posterior callus in the right valve 

 prominent and tooth-like, and the corresponding depression in the 

 left valve bordered by a slightly raised ridge. Pallial sinus deep, 

 extending to half the length of the shell. 



Long. Og, alt. 3, lat. 1| lines. 



Hub. Port Jackson. Dredged inside South Head Reef. 



o^ 



Alicia elegantula, u. s. (PI. XLIV. fig. 2.) 



Shell oblong, white, obsoletely concentrically plicate, very minutely 

 decussated, inequilateral ; anterior side three-fifths the length of 

 the shell, rounded ; posterior side roundly truncate, the dorsal mar- 

 gin concave, umbonal slope angulated ; ventral margin convex. The 

 hinge with the posterior callus almost obsolete. Pallial sinus deep, 

 extending to the umbones. 



Long. 54, alt. 3, lat. 1^ lines. 



Hab. Port Jackson. Dredged between Watson's Bay and " Sow 

 and Pigs" reef. 



Thracia modesta, n. s. (PI. XLIV. fig. 3.) 



Shell ovate, thin, white, rather ventricose, surface of valves irre- 

 gularly conceiftrically striate, inequilateral, beaks posterior ; anterior 

 side rotundate ; posterior side obliquely truncate, the dorsal margin 



