Erycina.] PELECYPODA. 921 



Genus 1. ERYCINA, Lamarck, 1804. 



Erycina, Lamarck, Ann. du Museum, vi, 1804, 413. Type : E. pellucida, 

 Lamarck. Not Erycina, Philippi, 1836, nor of Brown, 1833. Neceromya, 

 Gabb, 1873. 



Shell small, somewhat compressed or not very convex, exterior 

 concentrically striate, smooth, or rarely with partially radial sculpture, 

 sometimes punctate or sagrinate ; hinge with an obsolete external 

 ligament, sometimes hardly traceable, and a well-marked internal 

 resilium which is attached to the shell in an oblique, fossette behind 

 the beaks and close to the cardinal border ; teeth, normally, 1 or 2 

 minute cardinals and 2 lateral lamina 1 in each valve, the latter near 

 and sometimes confounded with the dorsal margin of the valve, usually 

 long, low proximally, more elevated distally, and often recurved upon 

 themselves, like a segment of a cylinder ; in the right valve sometimes 

 double, with the socket for the laminae of the opposite valve between 

 them. Pallia! line with a slight insinuation. (Dall.) 



Fossil in the Tertiary. 



KEY TO SPECIES. 



A. Anterior end produced and acutely rounded below, posterior end 



subtruncate. Sculpture : minute linear markings . . . . bifurca. 



B. Both ends regularly rounded. Sculpture : minute punctures . . parva. 



1. Erycina bifurca, Webster, 1908. Plate, 53. figs. '.. a. 



Kellia bifurca, Webster, T.N.Z.I., xl, 1907 (1908), 257, pi. 21, f. 24-29. 



Shell very small, inequilateral, somewhat quadrate, pale grey. 

 Beaks directed forwards, pointed, shining, prodissoconch and first 

 one-third of the shell white, translucent, and devoid of sculpture. 

 Anterior end slightly longer than the posterior, produced and acutely 

 rounded below ; posterior end short, subtruncate ; basal margin feebly 

 convex. Sculpture at first glance somewhat resembling E. parva, but 

 a closer examination reveals the linear markings, which, though ir- 

 regular, have one general direction ; the concentric growth-lines are 

 very marked, dividing the entire shell into bands, in each of which 

 the sculpture varies somewhat. ( Colour pale grey, white at the um- 

 bones. Interior with 2 clumsy patches of varying shape in different 

 specimens, extending downwards and outwards from behind the hinge ; 

 in young specimens these are milky, and may be seen through the 

 shell ; in mature shells these patches spread and thicken clumsily in 

 such a manner as to seriously diminish the capacity of the shell. 

 Hinge : 1 cardinal tooth in each valve, sometimes accompanied by a 

 small point under the umbo in the right valve and a clumsy thickening 

 of the margin in the left valve ; an anterior and posterior lateral in 

 each valve ; in some specimens a second posterior in each valve. No 

 external ligament, but a large posterior resilium. Pallial line entire. 



Diameter Ant.-post., 4mm.: dorso-ventral, 3-25 mm. : thick- 

 ness, 2 mm. 



