1880.] MR. E. A. SMITH ON THE GENUS MYODORA. 585 



not SO acute. The present species is more broad!)' and deeply 

 siilcated than M. striata, and of a different form, the hinder dorsal 

 slope being straighter and the anterior more curved. The deep 

 valve has not the elevated and strongly sculptured hinder marginal 

 ridge which is so characteristic of that species. 



17. Myodora antipodum, sp. nov. (Plate LIII. figs. 7, la.) 



Shell transversely elongate, broadly truncated behind, acuminately 

 curved at the opposite extremity. Anterior dorsal slope shorter 

 than the posterior, considerably oblique, rectilinear, hinder margin 

 feebly incurved. Deep valve rather shallow, concentrically lirate ; 

 lirae thickest near the anterior side, and less distinct posteriorly. 

 In the latter region a ridge runs from the umbo to the lower end of 

 the truncation ; and between this and the dorsal margin the surface 

 is concave. Flat valve very slightly concave, concentrically, 

 finely, and shallowly sulcate, the interstices on the front dorsal 

 margin being raised and prominent. Interior of valves with a single 

 impressed ray, curving from the uinbones to the lateral boundary of 

 the pallial sinus. The latter is broad and not deep. 



Length 9 millims., width 181, diam. 2. 



Hab. New Zealand {Col. Bolton, R.E.). 



This species may be known from M. boltoni by the broader 

 posterior truncated end, and the fact of the hinder dorsal slope being 

 longer than the anterior, whilst in that species it is the reverse. 

 The sculpture of the deep valve too is coarser, and the pallial sinus 

 broader and not so deep ; and the impressed ray meets the latter at 

 a different fioint. J/, pandoriformis has a curved front dorsal 

 margin, is more equilateral, its deep valve more convex ; and the 

 form is deeper from the umbones to the ventral margin. 



18. Myodora boltoni, sp. nov. (Plate LIII. figs. 9, 9ff, 96,9c.) 



Shell transversely elongated, much narrowed posteriorly, and 

 obliquely truncated at the end, broad and curved at the other 

 extremity. Anterior dorsal maigiu very slightly oblique, rectilinear, 

 posterior a little incurved, a trifle shorter than the other. Lower 

 or deep valve moderately convex, with a raised ridge from the umbo 

 to the lower end of the truncated extremity, and with a depression 

 between it and the raised margin. Surface almost smooth, with 

 the exception of the posterior end, which is distinctly sulcated, 

 especially upon the raised ridge and the margin. Upper or flat 

 valve somewhat concave, finely concentrically striated. Interior of 

 valves with a single impressed ray curving from the umbones to the 

 upper boundary of the pallial sinus. The latter is conspicuously 

 deep. Hinge-clavicle present. 



Length 9 milHms., width 14^, diam. 3. 



Hab. New Zealand {Colonef Bolton, R.E.). 



This species can hardly be compared to any of the known 

 forms. M. pandorifoj mis is more like i9 than any other; but that 

 is more strongly sulcated, m.ore broadly truncated posteriorly, more 



Proc. Zool. Soc— 1880, No. XXXIX. 39 



