306 [October, 1843. 



Pectunculus. 



P. parilis. Orbicular, slightly oblique; height and length equal ; posterior 

 superior margin obliquely subtruncated ; ribs denned by slightly impressed 

 narrow radii ; radiating striee minute and obsolete ; marginal teeth prominent. 



Locality. Cliffs of Calvert, Md. 



Differs from P. carolinianus, in being oblique, narrower towards the beaks, 

 less convex, and in the much less prominent ribs, &c. 



Pecten. 



1. P. biformis. Inequivalved; superior valve nearly flat; inferior ventricose ; 

 ribs 5 or 6, on the umbo, large, convex, with minute reticulated striee; from a 

 concentric sulcus below the umbo, the ribs suddenly become less prominent, 

 very wide and composed of fasciculi of smaller irregular ribs; ears equal, 

 small. 



Locality. Petersburg, Va. Mr. Tuofney. 



This singular Pecten is allied to P. decemnarius, but the peculiar character of 

 the ribs is a sufficient distinction. The lower valve, from which the description 

 is chiefly taken, has large convex ribs above, longitudinally striated, and sepa- 

 rated by a concentric groove from the numerous small ribs below ; the interstices 

 have smaller costoe ; young shells have the superior valve frequently slightly 

 concave. 



2. P. tricenarius. Suborbicular; inferior valve convex, ribs 30 to 33, some- 

 what unequal in size, crossed by minute lines ; sinus of the ear profound. 



Locality. Found with the preceding species by Mr. Tuomey. 



3. P. vicenarhis. Suborbicular, inequivalved, the superior valve ventri- 

 cose, the inferior plano-convex ; ribs about 20, somewhat flattened on the back ; 

 ribs of superior valve narrower and more distant than those of inferior valve ; 

 surface of both with crowded regular concentric wrinkles; ears equal, moderate 

 in size; sinus of inferior valve not profound. 



Locality. Wilmington, N. C. Mr. Hodge. 



Teilina. 



1. T.lenis. Subelliptical ; beaks medial ; anterior margin obliquely trun- 

 cated, the extremity acutely rounded ; dorsal margins equally oblique ; posterior 

 basal margin obliquely subtruncated; basal margin nearly straight in the middle 

 and towards the anterior extremity where it is arched ; the extremity consider- 

 ably above the line of the base ; posterior side with an oblique narrow fold. 



Locality. Cliffs of Calvert, Md. 



2. T. arctata. Ovate, thin, slightly ventricose along the umbonial slope ; 

 flattened in the middle of the valve ; dorsal and basal margins parallel ; pos- 

 terior margin rounded obliquely inwards ; basal margin slightly contracted in 

 the middle ; beaks slightly prominent ; posterior dorsal margin slightly sinuous ; 

 surface with concentric prominent acute lines ; cardinal plate rather wide ; 

 lateral teeth none. 



Found in North Carolina, by Professor Mitchell, of Chapel Hill. 



