1000 PELECYPODA. [Eulmnellibranchia. 



prosocoelous, the margins usually serrate or radially striated ; 

 adductor-scar subequal, the pedal distinct and usually distant ; 

 ligament and resilium parivincular, external, short, set in a groove ; 

 area obscure ; complete hinge consisting of an anterior and posterior 

 lateral in the left and 2 anterior and 1 posterior lateral in the right 

 valve, any or all of which may be absent ; 2 cardinal teeth in each 

 valve, the teeth simple, smooth, never bifid ; 1 cardinal in each valve 

 usually persistent, the other inconstant. 

 Trias to Kecent. 



Genus 1. PROTOCARDIA, Beyrich, 1845. 



Protocardia, Beyrich, Zeitschr. f. Malak., 1845, 17. Type : Cai'dium 

 hiUanuin, Sowerby (Cretaceous). 



Shell globose ; umbones elevated, incurved, and slightly inclined 

 anteriorly ; posterior area sharply distinguished by sculpture from 

 the rest of the surface ; right valve with 1 or 2 cardinal teeth. 2 

 anterior lateral teeth, and 1 or 2 posterior lateral teeth : left valve, 

 2 cardinal teeth, 1 anterior lateral tooth, and 1 posterior lateral ; 

 ligament external ; pallia! line entire. 



The genus is circumtropical. 



Sect. 1. NEMOCARDIUM, Meek, 1876. 



Nemocardium, Meek, Pal. Upper Missouri, 1870, 172. Type : Cardium 

 semiasperum, Deshayes. 



The posterior area spinose or tuberculate, the remainder of the 

 surface finely radially striate, or finely reticulate ; the anterior laterals 

 springing from the umbonal cavity. 



1. Protocardia pulchella, Gray, 184.>. Plate 62, tig. '.). 



Cardium pull-helium, Gray, Dieff. N.Z., 2.32 ; Conch. Icon., ii, 1844, pi. 8, 

 f. 42 ; Grit. List, 46. C. (Bucardium) pulchellum, Gray, Chall. Rep., 

 xiii, 161 ; Suter, T.N.Z.I., xxxiv, 222 ; Hedley, op. tit., xxxviii, 75. 

 Protocardia (Nemocardium) pulchella, Gray : Suter, T.N.Z.I., xxxix, 200 ; 

 xl, 358. Card-hint Ntrialulum, Sowerby, P.Z.S., 1840, 105, not of Brocchi : 

 Conch. Illustr., 1841, sp. 9, pi. 49, f. 16 ; pi. 177, f. 45 : Hanley, Cat. 

 Rec. Biv. Shells, 135, 363, pi. 17, f. 9 : Conch. Icon., ii, 1844, pi. 86^ f. 60 : 

 C.M.M., 73 : Crit. List. 4.5 : M.N.Z.M., 153 : Hedley, Mem. A.M., iv, 

 322. C. pulrhi-lluni. Gray : Pritchard and Gatliff. P.R~.S. Vic., xvi (n.s.), 

 136. 



Shell small, subcordate, somewhat oblique, rather ventricose, 

 inequilateral, thin, finely radially striate. pale fulvous with pink 

 striped bands. Beaks raised, convex, faintly biangulate. a little ex- 

 cavated in front, contiguous, the sharp points incurved and slightly 

 turned forwards. Anterior end shorter, regularly convex ; posterior 

 end truncated, the dorsal margin gently sloping, ventral margin 

 broadly rounded. Sculpture consisting of very fine and dense, regular, 

 rounded radial riblets, the interstices of the same width as the ribs, 

 crossed by very fine, wavy, and anastomosing concentric threads, 

 raised into short spines on the riblets of the posterior part of the 



