﻿326 CONRAD'S DESCRIPTIONS OF 



MERETRIX, Lam. 



Meretrix tippana. PI. 34, fig. 18. Subtriangular, obsoletely striated concen- 

 trically; anterior side slightly compressed, with an ascending basal margin, extremity 

 rather acutely rounded, distant from the apex ; base a little prominent in the middle 

 subtruncated on either side ; posterior end but slightly more obtuse than the anterior 

 beaks prominent. 



PAPYRIDEA, Swains. 



Paptridea bella. Suboval, very thin and fragile, ventricose ; radii angular, promi- 

 nent, about 30 in number, towards the extremities minutely tuberculated ; ribs obso- 

 lete near the buccal end ; basal margin somewhat salient opposite the umbo ; trun- 

 cated posteriorly ; anal end truncated, nearly direct. 



This species is proportionally shorter than the elegantulum or protextum. The 

 largest specimen in Dr. Spillman's collection is not so large as those species usually 

 are. Received since the plates were finished. 



There are two other species of this genus in the inferior Cretaceous marls. Papyridea 

 (Cardium) elegantulum, Roemer, and P. {Cardium) protextum, Con. 



CARDIUM, Lin. 



1 Cardium tippanum. PI. 34, fig. 8 h. Cordate, profoundly ventricose, rather thick ; 

 umbo and summit prominent ; ribs flattened, little prominent, tricarinate, armed with 

 prominent erect spines ; in the intercostal space is a row of minute tubercles, except 

 on the posterior side, where a prominent intercostal line appears. 



A mere fragment, so well marked, however, that the description and figure will 

 characterize the species. 



2. Cardium ripletense. A small cordate species, with minute equal radii, between 

 each of which is a series of comparatively long hair-like spines. 



Subgenus LiEVICARDIUM, Swainson. 



3. Cardium Spillmani. PI. 34, fig. 3. Oblong or profoundly elevated, inequilateral, 

 profoundly ventricose ; umbo and summit elevated ; beaks nearly contiguous ; surface 

 with distant irregular grooves on the anterior side, and 3 to 5 radiating slightly 

 impressed furrows on the umbonal slope. 



Length 2$ inch. Height 4| inch. 



A large and remarkably elevated species with a very thick hinge and profound 

 teeth. The surface is smooth and only ribbed about the umbonal slope, and on the 

 posterior side of the umbo where in one specimen are about 18 radii; those behind 

 the umbonal slope fine and indistinct without the aid of a glass. Named in honor of 

 Dr. W. Spillman. 



