708 SYSTEMATIC PALEONTOLOGY 



The group is restricted to the Cretaceous. 



A. Latitude of adult shell rarely exceeding 25 mm.; outline ovate-tri- 



gonal Cymbophora berry i 



B. Latitude of adult shell exceeding 25 mm.; outline high-trigonal. 



Cymbophora wordeni 



SPISULA (CYMBOPHORA) BERRYI n. sp. 

 Plate XLIII, Figs. 2, 3 



Description. Shell very thin and fragile, rather small for the genus, 

 transversely ovate-trigonal in outline, smoothly inflated; umbones small 

 but rather prominent, evenly rounded, overtopping the dorsal margin, the 

 apices incurved and feebly prosogyrate, medial or slightly anterior in posi- 

 tion; umbonal angle 1 usually exceeding 90; dorsal margins oblique or 

 somewhat convex, the anterior slope as a rule a little more gentle than the 

 posterior ; anterior extremity rather narrow but symmetrically rounded ; 

 posterior obscurely truncate obliquely ; base line quite strongly and sym- 

 metrically arcuate; external surface sculptured with faint, incremental 

 striations, less feeble and more crowded toward the ventral and lateral 

 margins ; anterior area cut off by a shallow and sublinear depression which 

 persists from the umbones to the base; incremental sculpture much less 

 feeble in front of the sulcus than behind it ; posterior area evenly rounded 

 but differentiated by a linear liration which margins a cuneate area ; area 

 clearly differentiated by the very fine evenly crowded concentric stria 1 ; 

 incremental behind this oblique wedge the most elevated of any on the 

 shell; resilium lodged in a spoon-shaped chondrophore beneath the 

 umbones, posteriorly directed, its margins raised and quite strongly rein- 

 forced; hinge armature rather concentrated, two cardinals in the right 

 valve, partially fused beneath the umbones and diverging at an angle of 

 little less than 90, anterior arm very close to the dorsal margin and 

 diverging from it at a very small angle, posterior arm at the margin of 

 the chondrophore; laterals double, the dorsal lamina distinct from the 

 dorsal margin though fused with it basally ; inner faces of clasping laterals 

 transversely striated ; left cardinal short but heavy, A -shaped ; left 

 laterals double, the inner lamina? elevated and flattened upon their sum- 

 mits, transversely striated ; adductor muscle scars rather small and 



