i6 



6. Nucula {Nuculd) exodonta sp. nov. (Plate I, figs. 5, 6). 



The following is a description of this new species : — Shell small, trigonal, subequilateral, 

 moderately, inflated, thin, escutcheon depressed, small, subcordate ; obtuse, formed by incurved 

 umbones, anterior edge somewhat curved running gradually into obliquely truncate end ; posteriorly 

 subangLilate ; ventral margin distinctly arched ; sculpture consisting of sharp concentric rugae 

 just visible to naked eye ; hinge for size of shell heavy, anterior serjes consisting of 1 1 teeth, 

 almost in straight Une, posterior séries slightly arched formed by 7 teeth ; lower inner margins 

 of valves smooth. Shell of a light horny colour ; nacre white iridescent. 



Measurements : — Length 4.7 mm., height 3.5 mm., diameter 2.6 mm. 



Habitat: — A single spécimen, the Holotype of the species, was trawled at St. 300 

 (io°48'.6S., i23°23'.iE., 918 mètres). 



Remarks: — Nucula [Nticula) exodonta is a beautiful species, and is easily recognised 

 by its form and sculpture. 



7. Nucula {Nucula^ bathybia sp. nov. (Plate I, figs. 7, 8). 



The following is a description of this new species : — Shell médium sized, obliquely 

 ovate, inequilateral, thin, subcompressed ; escutcheon slightly depressed, narrowly triangular ; 

 apex obtuse ; umbones slightly tumid, curved inwards and backwards ; anterior side much longer 

 than posterior, convex, narrowly rounded towards very arched basai margin ; posterior side 

 much shorter, slightly curved \ posterior end broadly rounded ; sculpture consisting of microscopic 

 concentric sulcations; hinge-plate narrow, teeth moderately strong, anterior séries consisting of 

 12, posterior of 6 teeth, both séries almost straight. Shell of a light yellow colour, nacre pearly, 



iridescent. 



Measurements (in millimètres) : 

 Holotype 



Length 8 6.5 



Height 6.1 5.4 



Diameter 4 1.8 (single right valve). 



Habitat : One complète shell, the Holotype of the species, and three odd valves were 

 brought up in a deep sea trawl at St. 208 (5° 39' S., 122° 12' E., 1886 mètres). 



Remarks : — Nucula [Nuctila] bathybia is allied to N. (A^.) strangei A. Adams ^) but 

 its shape, sculpture and hinge offer good distinguishing characters. 



8. Nucula [Nuczila] pachydonta sp. nov. (Plate I, figs. 9, 10). 



The following is a description of this new species : — Shell small, trigonal-elliptical, very 

 inequilateral, ventricose, thick, solid ; escutcheon area only slightly concave ; umbones very tumid, 

 prominent, curved backwards and inwards, hardly meeting in middle line ; anterior side sloping, 

 very convex, broadly curving towards slightly arched basai margin ; posterior side much shorter, 

 acuminated below ; sculpture consisting of very minute, regular concentric striae ; hinge-plate 



i) Adams, A. — Proc. Zool. Soc. London, (Vol. for 1856), p. 52 (1856). 



