218 TANDORID^. 



L. PLicATA, Montagu, 



Mytilus jAicatus, Mont, (not Chemn.) Test. Brit. Suppl. p. 70. — Laskey, 

 Wern. Mem. vol. i. pi. 8, f. 2. — Turt. Conch. Diction, p. 

 114. 



Saxkava plicata, Turt. Dithyra Brit. p. 22. 



The shape is more or less rhomboidal, but evidently variable, 

 from a liability to distortion ; it is excessively inequilateral, being 

 truncated in front, and dilated and produced behind. The valves 

 seem very nearly, if not quite equal, and are thin, but not trans- 

 parent, of a subnacreous white, veiled, when perfect, with a pale 

 yellowish drab-coloured epidermis, beneath Avhich the surface is 

 almost smooth, or, at most, rather distantly antiquated by the 

 concentric layers of growth. The convexity is unequally dis- 

 tributed, the chief elevation, amounting at times to tumidity, 

 being subcentrally from the vimbones to the posterior side of the 

 ventral margin ; the upper area of the posterior side, as well as 

 the front extremity, is considerably more depressed. The ventral 

 margin, which varies from slightly retuse to actually inflected in 

 front, is more or less arcuated behind. The anterior edge abruptly 

 slopes from the beaks in a more or less straightish line, (at times 

 subretuse, at times a little convex,) causing the extremity of the 

 almost truncated anterior side to appear abbreviately subcuneiform, 

 or rectangular below. The termination of the elongated posterior 

 side is more or less angulated above, and obliquely rounded be- 

 low, the chief projection being more adjacent to the dorsal than 

 to the ventral margin ; the former is produced, more or less 

 ascending, and in the more naturally developed examples straight- 

 ish, but occasionally convex, or even arcuated. The umbones 

 project a little above the dorsal outline ; the beaks are small, and 

 much incurved, (in one specimen they lean a little forward,) in 

 front of them is situated a large and distinct lunule-like impres- 

 sion. The interior is of a silvery pearl, the hinder dorsal edges 

 are not inflected, and the hinge plate resembles that of cxineata. 



The ossicle of the specimens from whence we have drawn up 

 the above description, is unfortunately wanting. The larger in- 

 dividuals were about five-sevenths of an inch in length, and at 

 most half an inch in breadth. They appear most nearly allied to 

 cuneata, which diff"ers from them in the absence of a lunule, and 

 in the attenuation of its hinder side. 



