Perrierina.] PELECYPODA. ( .0l 



the posterior arm shorter, with about 5 oblique lateral lamellae in front 

 and 7 to 9 behind ; left valve with 1 short curved median cardinal, 

 which does not reach to the dorsal margin, and 2 oblique cardinals, 

 one anterior and one posterior, which extend to the dorsal margin 

 but are not united ; the lateral lamellae as in the other valve. Liga- 

 ment internal, oblique, short, and narrow, a little behind the prodisso- 

 conch. Adductor-scars unequal, the anterior pyriform, the posterior 

 roundish. Pallial line entire, simple. 



Length, 3-5 mm. ; height, 2-5 mm. (type). 



Type in the Mus. Hist. Nat., Paris. 



Hob. Stewart Island, in 35 fathoms, type (Filhol) ; off Wreck 

 Reef, in 50 fathoms (E. R. Waite) ; oft" Otago Heads (A. Hamilton) ; 

 Snares, in 50 fathoms (Captain Bollons) ; Whangaroa Harbour (C. 

 Traill). 



Genus 4. CUNA, Hedley, 1902. 



Ciuin, Hedley, Mem. A.M., iv, pt. o, 29, -fuly, 1902, 314. Type : C. concen- 

 trii-n, Hedley. Cuna, Dall, Trans. Wagn. Krcv Inst., iii, pt. 6, 1467. 



Shell very small, equilateral or slightly rostrate, higher than long, 

 with lunule and impressed dorsal area, beaks erect, prodissoconch 

 marked, valves sometimes, clasping. (Sculpture radiate or concentric, 

 or both. Inner ventral margin usually denticulate. Hinge - plate 

 broad and flat ; in the left valve 2 well-developed cardinals ; in the 

 right a rudimentary cardinal and a massive projecting flat-topped 

 and triangular cardinal. Laterals produced, sometimes transversely 

 striated, a posterior and an anterior in each valve ; posterior right 

 and anterior left lateral margins fitting into sockets in the margin 

 of the opposite valve. Resilium internal, behind the right posterior 

 cardinal. Pallial line entire. 



Distribution. New Zealand, Tasmania, Australia, and Japan ; in 

 deep water. 



Fossil in the Claibornian Eocene, Alabama. 



KEY TO SPECIES. 



A. Shell with prominent close radiate riblets, about 15 ; interstices 



narrow . . . . . . . . . . . . carditelloides. 



B. Shell with faint and narrow distant radiate riblets, about 10 ; 



interstices broad . . . . . . . . . . delta. 



1. Cuna carditelloides, Suter. Plate 52, fig. 13. 



Cuna carditelloides, Suter, Sci. Results N.Z. Govt. Trawling Exp., 1907, pt. 2. 



Shell minute, trigonal, solid, slightly inequilateral, radially costate. 

 Beaks contiguous, prodissoconchs minute, globose, and smooth, sur- 

 rounded by a narrow groove. Anterior end with the dorsal margin 

 straight, descending, rounded towards the convex basal margin ; 

 posterior end similar to the anterior, but the dorsal margin feebly 

 curved and angled towards the basal margin. Lunule distinct, long, 

 lanceolate, with a few concentric ridges. Sculpture consisting of about 



