1880.] 



MR. E. A. SMITH ON THE GENUS MYODORA. 



587 



21. Myodora tenuisculpta, sp. nov. (Plate LIII. figs. 11, 

 11a.) 



Shell thin, ineqviilateral, abruptly truncated behind, and sharply 

 rounded at the other end ; anterior dorsal slope rectilinear, longer 

 than the posterior ; the latter is remarkably incurved. Deep valve 

 only slightly convex, with a very feeble depression posteriorly, and with 

 very shallow concentric sulci, scarcely apparent to the naked eye. 

 Flat valve a trifle concave, concentrically finely striated. Impressed 

 ray of the interior curved, meeting the inner boundary of the mantle- 

 impression in the flat valve and falling a little further within in the 

 deep valve. Posterior scar subrotund ; anterior elongate, much 

 narrower. 



Length 5 millims., width 7, diam. 1|. 



Hah. ? 



This is the most finely sculptured species in the genus, and is less 

 equilateral than M. reeveana. 



22, Myodora compressa, sp. nov. (Plate LIII. figs. 12, 12a.) 



Shell compressed, rather thin, subtrigonal, posteriorly obliquely 

 truncated, acutely rounded in front. Hinder dorsal slope rather 

 incurved, shorter than the anterior, the latter being nearly rectilinear. 

 Ventral curve slight. Lower or deep valve very shallow, with a feehle 

 depression posteriorly near the margin, and marked with shallow 

 concentric sulci and striae, the interstitial ridges being most prominent 

 at a short distance from the hinder extremity, or, in other words, on 

 that part of the surface which bounds the depression. Angle formed 

 by the truncated end and the dorsal margin rather abrupt, of about 

 90 degrees. Upper valve flat, with a shallow depression posteriorly, 

 finely concentrically striated. Impressed ray of the interior curved 

 a little, extending in the flat valve to the inner boundary of the pallial 

 sinus, and a little nearer the centre in the other valve. 



Length 7-^ millims., width 9, diam. 1|-. 



Hab. ? 



This is a very compressed species, and very finely sculptured. 

 It is thinner than M. proximo, with a straighter anterior dorsal 

 margin, more finely sulcated upon both valves, broader and flatter. 

 It is hardly so finely sculptured as M. tenuisculpta, and of a different 

 form, being much less elongated transversely. 



EXPLANATION OF PLATE LIII. 



Figs. 



1, la. Myodora 

 p. 582. 



ohlonga, 



2, 2a. ovcda, p. 582. 



3, 3a. • trigona, p. 582. 



4, 4a. plana, p. 582. 



6, 5aj 5b. novcB-zealandiiB, 



p. 584. 



6, 6a, 6J, 6c. &ubrostrata,bM. 



7, 7a. antipodum, 



p. 585. 



Figs. 8, 8a, Sh. Myodora proximo, 

 p. 686. 

 9, 9a, 9J, 9c. holtoni, p. 585. 



10, 10a. reeveana, p. 586. 



11, 11a. tenuisculpta, 



p. 587. 



12, 12a. compressa, 



p. 587. 



39^ 



