OF CONCIIOLOGY. 75 



vated recurved lamelliform concentric distant ribs on the disk, 

 and two or three small ribs on the umbo ; posterior slope wide 

 and flattened or concave, forming a right angle with the disk ; 

 umbonal slope terminal. 



Locality. — Iladdonfield, N. J, 



I found one valve of this singular species nearly entire. 



CARDIUM, Lin. 



Subgenus Criocardium, Conrad. 



INIultiradiate ; interstices spinose, ribs smooth ; anterior lateral 

 tooth long and prominent. 



This subgenus presents a singular deviation from the char- 

 acter of recent spinose species, in having long, slender spines 

 in the interstices between the ribs, while the ribs are smooth. 



C. DUMOSUM, Conrad. 



Description. — Cordate equilateral, ventricose ; umbo broad ; 

 summit very prominent; ribs very numerous, small, closely ar- 

 ranged, convex ; interstices furnished with numerous long slender 

 spines ; posterior margin subtruncated or slightly convex ; height 

 1^ inch ; length the same. 



Locality. — Haddonfield, N. J. 



I am not certain whether or not this is C. multiradiatum, 

 Gabb. It has a much broader umbo than multiradiatum is repre- 

 sented to have. It also closely resembles C. liaulineanum, 

 D'Orb., but is much larger, and proportionally more elevated, 

 and agrees with it iri having the spines in the interval between 

 the ribs. The two species, therefore, must be referred to the 

 one subgenus, which appears to be limited to the Cretaceous 

 strata. 



SOLYMA, Conrad. 

 Hinge cliaracter. Two direct approximate teeth under the 

 apex of right valve. The anterior tooth thick and rounded an- 

 teriorly. 



Locality. — Haddonfield, N. J. 



This genus is allied to LeptoSolcn.) Conrad, but wants the in- 

 ternal rib of that genus ; and differs also in having two teeth in 

 the right valve. 



S. LiNEOLATUS, Conrad. — PI. 3, fig. 9. 



Description. — Equilateral, ventricose, substance very thin ; 

 anteriorly slightly contracted, end margin rounded ; posterior 

 margin obtusely rounded ; umbonal slope rounded; ventral mar- 



