329 

 3- Cuspidaria [Cuspidarid] convexa sp. nov. (Plate VII, fio-s. 36, 37). 



Cîispidaria {Cuspidarid) convexa is closely allied to C. (C.) mitis described above, but 

 its shell is more oblique and the anterior dorsal margin of the valves, which is very short, is 

 hardly differentiated from the anterior margin. The valves are more tumid and the umbones, 

 which are greatly inflated, are curved inwards and backwards. The rostrum is deeper but 

 comparatively shorter and less convex, and the rostral ridge is not so raised. The sculpture is 

 coarser and not so regular as in C. (C.) mitis. 



Measurements of Holotype : — Length 16 mm., height io.8 mm., diameter 10 mm., 

 length of rostrum 5.8 mm., depth of rostrum 4 mm. 



Habitat: — The unique Holotype was brought up in a trawl at St. 314 (7° 36' S., 

 II 7° 30'. SE., 694 mètres). 



4. Cuspidaria (Cuspidaria) gigaittea sp. nov. (Plate VII, fig. 38). 



The following description of C. (C) gigantea — probably the largest known species of 

 the genus — is unfortunately based on a single, dead, right valve only : — Species of a large 

 size; shell oblique, ovate-rostrate, inequilateral, moderately convex, thick, solid; slightly rounded 

 in front, with a long comparatively narrow rostrum behind ; umbones only slightly elevaled, 

 somewhat tumid, situated much behind middle of shell; anterior dorsal margin greatly arched, 

 posterior dorsal short, not very concave, ventral margin very convex, marked off from ventral 

 border of rostrum by a broad depressed area ; rostrum almost half the entire length of shell, 

 narrow, tubular, concave above, curved outwards and downwards; rostral ridge distinctly marked, 

 not very sharp ; sculpture consisting of very regular, minute thread-like concentric striae; thèse 

 become irregular on the rostrum. A single elongate posterior latéral tooth ; fossette deep, 

 posteriorly inclined and attached to hinge-margin by its posterior edge. Shell of a dirty gray colour. 



Measurements of Holotype: — Length 52 mm., height 26.8 mm., diameter of single valve 

 8.7 mm., length of rostrum 25.5 'mm., depth of rostrum 5 mm. 



Habitat: — A single right valve, the Holotype of the species, was dredged at St. 159 

 (o°59^I S., 129° 48^.8 E., 411 mètres). 



Remarks : — The large oblique, ovate shell with a beautiful concentric sculpture and an 

 elongate, tubular, curved rostrum distinguish C. gigantea from ail other species of the genus 

 Cuspidaria. 



5. Cztspidaria [Citspidaria) corrtcgata sp. nov. (Plate VII, fig. 39). 



The following is a description of this new species : — Species of a moderate size, shell 

 inequilateral, ovate, thick ; rounded in front, shortly rostrate behind ; umbones acute, depressed ; 

 anterior dorsal margin convex, posterior dorsal strongly incurved, concave ; ventral margin arcuate, 

 curving up suddenly from about middle ; rostrum short, marked off by an oblique dépression 

 with well developed oblique ridge ; surface obliquely ridged, ridges low, narrow, rather distantly 

 separated, more regularly concentric anteriorly ; sinuous and running into one another near the 

 rostrum, rostrum coarsely rugose \ hinge as in typical Cztspidaria. Shell of a whitish colour, 

 nacre shiningr white. 



SIBOGA-EXPEDITIE Llllr. 42 



