334 



with the description and figures of C. {P.) thaumasia Sturany from the Red Sea, that I hâve 

 no hésitation in identifying it with this species. 



The shell is subtrigonal, moderately inflated shortly rostrate posteriorly and is covered 

 with regular, close, concentric, low ridges. The hinge of the left valve agrées with Sturany's 

 description, while the hinge area of the right valve is broken. 



The "Siboga" shell was, as noted above, brought up in a trawl at St. 306 (8° 27' S., 

 122° 54'. 5 E., 247 mètres). 



Genus Myonera Dali & Smith. 



1886. Myonera Dali & Smith in Dali, Bull. Mus. Comp. Zool. Harvard, XII, p. 302. 

 1903. Myonera Dali, Trans. Wagner Free Inst. Philadelphia, III, p. 1505. 



With Dall I consider Myonera to be a genus of equal rank to Cuspidaria Nardo. The 

 génotype of Myonera is Myonera paucistriata (Dall). 



I. Myonera dautzenbergi sp. nov. (Plate VII, fig. 51). 



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

 inequilateral, trigonal, shortly but broadly rostrate postefiorly, thin, greatly inflated ; rounded in 

 front, umbones prominent, incurved, almost meeting in middle line ; anterior dorsal margin sloping, 

 almost straight ; posterior dorsal with upper margin of rostrum slightly concave, ventral slightly 

 arcuate ; rostrum short, deep, subtruncated posteriorly, without rostral ridges ; surface sculpture 

 consisting of regular, low, concentric almost microscopic striae, anteriorly some of the striae 

 more raised and appearing as strong ridges ; hinge edentulous, fossette posteriorly dissected. 

 Shell of milk white colour. 



Measurements of Holotype : — Length 15 mm., height 11.5 mm., diameter 8.8 mm. 



Habitat : — The Holotype and two stray valves of this interesting species were brought 

 up in a deep-sea trawl at St. 52 (9° 3°. 4 S., 119° 56^.7 E., 959 mètres). 



