900 PELECYPODA. [Eulamellibranchia. 



the characters as described for the genus. Resilifer very oblique. 

 Pallial line simple, not interrupted. 



Length, 4-5 mm. ; height, 3mm. ; diameter, 1-8 mm. 



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



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

 Strait, in 15 fathoms (A. Hamilton) ; Bounty Islands, in 50 fathoms 

 (Captain Bollons) ; twenty-one miles and a half north-east of Wreck 

 Reef, in 50 fathoms ; twenty-four miles south-east of Long Point, 

 in 120 fathoms (E. R. Waite). 



Var. truncata, Suter. Plate 52, fig. 1 1 . 



Cyamiomactra problematica, Bernard, var. trtn/cata, .Suter, Sci. Results N.Z. 

 Govt. Trawling Exp., 1907, pt. 2. 



Differs from the species in the short subtrapezoidal form ; the 

 anterior end being short and rounded, the posterior end truncate, 

 with a distinct angle towards the basal margin ; between this and the 

 beaks the valves show a distinct angle. It is an extreme form of the 

 variable species, and well worthy of a varietal distinction, though 

 intermediate forms are sometimes met with ; they, however, are never 

 so distinctly angled. 



Length, 4 mm. ; height, 3-5 mm. ; diameter, 2 mm. 



Type in the Canterbury Museum, Christchurch. 



Hob. Twenty-one miles and a half north-east of Wreck Reef, in 

 50 fathoms (type) ; dredged at Waitangi, Chatham Islands (E. R. 

 Waite) ; Bounty Islands, in 50 fathoms (Captain Bollons). 



Genus 3. PERRIERIXA, Bernard, 1897. 



Perrierina, Bernard, Bull. Mus. Hist, Nat., Paris, 1897, No. 7, 312. Type 

 and only known species : P. taxodonta, Bernard. 



As there is only one species known, the characters of this must, 

 for the present, be also those of the genus. 



1. Perrierina taxodonta, Bernard, 1897. Plate 52, figs. 12, a, b. 



Perrierina taxodonta, Bernard, Bull. Mus. Hist. Nat., Paris, 1897, No. 7, 

 312, f. 3 in text. 



Shell very small, thin and fragile, oblong, equivalve, inequilateral, 

 smooth, pellucid. Beaks with a large round prodissoconch, well marked 

 off from the rest of the disc, not prominent, slightly directed forward. 

 Anterior end shorter, very narrowly convex, the dorsal margin short, 

 straight, descending ; posterior end broadly and regularly curved, the 

 dorsal margin faintly rounded and very slowly descending ; basal 

 margin strongly convex, ascending in front. Sculpture : None. Epi- 

 dermis thin, shining. Colour pale-yellowish, mostly with distant 

 brown divaricating bands. Interior smooth, shining, showing the 

 colour-markings. Margins smooth, sharp. Hinge-plate very narrow, 

 long ; right valve with a A -shaped cardinal in front of the resilium, 



