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Show 1880.] MR. E. A. S M I T H O N T H E G E N U S M Y O D O R A . 585 not so acute. The present species is more broadly and deeply sulcated 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 umbones to the lateral boundary of the pallial sinus. The latter is broad and not deep. Length 9 millims., width 1 3-1-, 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 point. M. 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, 9a, 9b, 9c.) Shell transversely elongated, much narrowed posteriorly, and obliquely truncated at the end, broad and curved at the other extremity. Anterior dorsal margin 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 strutted. 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 millims., width 14£, diam. 3. Hab. New Zealand (Colonel Bolton, R.E.). This species can hardly be compared to any of the known forms. M. pandoriformis is more like it than any other; but that is more strongly sulcated, more broadly truncated posteriorly, more PROC. ZOOL. Soc-1880, No. XXXIX. 39 |