1036 PELECYPODA. [Septibranchia. 



1 



Shell subequivalve, rostrate, earthy, or cellule-crystalline, rarely 

 with surface granulations ; hinge edentulous or with subumbonal 

 tuberculation, sometimes buttressed ; resilium internal, with a mesial 

 or ventral lithodesma ; area amphidetic or obscure ; valves closed, 

 except at the tip of the rostrum ; pallia! line simple. 



Jura to Recent. 



Genus 2. CUSPIDARIA. Nardo. 1840. 



Cuspidaria, Nardo, Revue Zool., 1840, 30 ; Dall, Bull. Mus. Comp. Zool., 

 xii, 1886, 292. Type : Tellina cuspidatn, Olivi. Necera, Gray, 1833 ; 

 not of R. Desvoidy, 1830. 



Animal with unequal siphons, united at their bases, surrounded 

 by a small number of tentacles bearing cupules at their tips ; anal 

 siphon with a tub alar valve. 



Shell pyriform, white, with an epidermis, a little inequivalve, the 

 right valve being usually a little smaller and less inflated, inequi- 

 lateral, rounded and globose in front, rostrate and slightly gaping 

 behind ; external ligament elongated, linear ; resilium in a small 

 spoon-shaped resilifer which is vertical or obliquely directed back- 

 ward and its hind part confluent with the hinge-plate ; the lithodesma 

 distinct, semicircular ; teeth of the hinge not constant a small 

 cardinal tooth sometimes in front of the resilifer, and a posterior 

 lateral tooth usually well developed in the right valve, but obsolete 

 in the left ; a reinforcing clavicle descends occasionally from the 

 umbonal cavity ; adductor-scars large ; pallial line with a feeble sinus. 



Distribution. All seas, but more abundant in the abyssal zone, 

 one species (C. lucifuga, Fischer) having been obtained by dredging in 

 2,731 fathoms. 



Fossil. Secondary and Tertiary. The genus appears in the 

 Eocene of Australia, and very likely migrated to New Zealand. 



KEY TO SPECIES. 



A. Shell concentrically finely striated, no radial ridges on the rostrum Fairchildi. 



B. Shell with concentric sharp laminae, rostrum radially ridged . . Trailli. 



1. Cuspidaria Fairchildi, Suter, 1908. Plate 54, figs. 16, a. 



Cuspidaria Fairchildi, Suter, T.N.Z.I., xl, 1907 (1908), 372, pi. 29, f. 19. 



Shell small, thin and fragile, ovate, with a long and straight 

 posterior rostrum, concentrically finely striate, almost equivalve, in- 

 equilateral. Beaks small, sharply pointed, directed forwards, situate 

 a little in front of half the length ; prodissocouch small, roundly 

 ovate, smooth. Anterior end narrowly rounded, the doisal margin 

 slowly descending, straight ; posterior end produced into a long 

 straight rostrum, gaping at its end ; basal margin broadly rounded, 

 slightly concave in front of the rostrum. Lunular area very little 

 excavated. Sculpture consisting of very fine and dense concentric 



