356 



aaJ each one slightly notches the ventral margin on its outer 

 aspect, the notches of successive grooves being more anterior. 

 In very young living shells the grooves are very deep at the 

 anterior margin, so as to form distinctly projecting lamellae 

 here. The prominent prodissoconch is well preserved as a 

 tiny concentrically hollowed cap. 



Cuna delta, Tate and May, sp. 



Carditella delta, Tate and May, Trans. Roy. See, S. Austr., 

 vol. xxiv., 1900, p. 102. 



Cuna delta. Tate and May. Verco, Trans. Roy. See, S. 

 Austr., vcl. xxxi., 1907, p. 109. See references there. 



Dredged also in 104 fathoms, thirty-five miles south-west 

 off Neptunes, and in 130 fathoms off Cape Jaffa, one valve 

 at each station. Its habitat is evidently in the shallower 

 water, not beyond 22 fathoms. 



Cuna cessans, n. sp. PI. xiv., f. 4 to 7. 



Shell rather thin, trigonal, almost equilateral. Umbonal 

 angle rather less than a right angle. Apex capped by a 

 minute prodissoconch. Dorsal borders nearly straight, tne 

 posterior barely excavate, the anterior barely convex. An- 

 terior and posterior ventral angles well marked. Ventral 

 border convex, not crenulated. Exterior dull, rough, sordid, 

 with about ten obsolete radials; and several concentric imbri- 

 cations or growth-rests, besides obsolete accremental striation. 

 Anterior and posterior sides somewhat excavate into long 

 lunule and escutcheon, the posterior more deeply than the 

 anterior. The right valve has a large triangular cardinal 

 tooth, and a small posterior above and behind the ligamental 

 pit. The left valve has a large anterior cardinal, and a 

 depression behind the socket of the right wedge tooth for 

 the ligament, separated by a tooth, and a small one above 

 and behind the pit. Each valve has a marginal lateral, and 

 a lateral separated from the margin by a groove. The in- 

 ternal ventral border is not denticulate. The interior is 

 white with the ribs and imbrications visible through the 

 shell. Colour is a dull light horn tint. 



Dim. — Antero-posterior diameter, 18 mm. : umbo-ven- 

 tral, 2*1 mm. : sectional, '9 mm. 



Dredged in Backstairs Passage, 22 fathoms, several alive 

 and valves. 



Diagnosis. — Its closest ally is (J. delta, Tate and May; 

 but it is less solid, has a wider umbonal angle, has a smaller 

 sectional diameter, has the concentric rest gradations, and 

 no marginal denticulations. 



Type in Dr. Verco's collection. 



