INVERTEBRATE PALEONTOLOGY. l('). r ) 



are remains of two prominences that have the appearance of being casts of two 

 somewhat diverging cardinal teeth in the right valve, with impressions for 

 two other cardinal teeth in the left; hence, so far as can be made out, the 

 teeth of the hinge seem to agree with those of the last-described species.* 

 Specifically, however, this form di tiers from the last in its more depressed and 

 transverse outline as well as in having its lateral extremities more nearly 

 equal and more narrowly rounded; the posterior margin not being truncated 

 as in the last. 



Locality and position. — Same as last. Collected by Professor Mudge. 



CARDIID^. 



Genus CARDIUM, Linnaeus. 



Synou.— Cardium, Linnaeus (1758), Syst. Nat., 10th ed.,678.— O. F. Mttller ( 177(1), Zo.il. Dau. Prodi-., xxx.— 

 Fabr. (1780), Fauna Groml., 409.— Brug. (1789), Encyc. Moth., I, 203.— Lam. (1799), 

 1'roilr., SO; and (1801), Syst., 119— Oken (1835), Allg. Naturg., V, 314.— Philippi (1836), 

 Moll. Sic, I, 49.— Agassiz (1839), Moul. de Moll., 35.— Swaiusou (1840). Malac, 373; 

 and of nearly all later authors on conebology. 



Acathocardia, Gray (1847). 



Trachicardium, Morch (1853), Cat. Yoldi, 53. 



Cerastoderma (Poli), Morch (1853). ib., 34. 



Tropidoeardium, Roeuier (18G8), Marteni and Chemnitz, Syst. Conch.-Kab., I, 13. 



Criocardium, Conrad (1870), Am. Jour. Conch., VI, 75 (as a subgenus of Cardium). 



I'lvluncuhts (Adanson), Stoliczka (1870), Palasont. Indica (as a subgenus of Cardium; not La- 

 marck and others i. 



Elt/m. — Kapiia, the heart. 



Examp. — Cardium aciileatum, Linn. 



Shell globose-cordate, or nearly vertically or somewhat obliquely sub- 

 oval, rarely transversely suboval, of variable thickness ; valves nearly equilat- 

 eral, more or less gaping, and dentate or serrated behind, or closed and merely 

 crenate along the free margins within ; surface variously costate or striate, 

 and often roughened by short spines, or other asperities; hinge typically with 

 two cardinal teeth to each valve, so arranged as to cross when the valves are 

 closed; cardinal and lateral teeth subject to more or less variation ; pallial 

 line nearly simple, or very slightly sinuous. 



The foregoing diagnosis and synonymy are made to include a number 



* Of course, if all of the indentations seen in the cast of the binge figured were natural, this would 

 certainly not lie a Corbicula; but it is evident th»,1 these an- partly due to the accidental erosion of the 

 hinge lii-toii- the shell was enveloped in the sand. 



