NATURAL SCIENCES OF PHILADELPHIA. 327 



into the anal border, which is subtruncate and most prominent above. Basal 

 edge broadly emarginate. Surface marked by numerous, irregular, concentric 

 lines. 



Length, -25 in. Width, -55 in. Diameter, -3-5 in. 



Length of tube, -9 in. 



Not rare in the marls of New Jersey. I found one specimen, somewhat 

 smaller than the above measurements, at the point where the West Jersey 

 railroad crosses Big Timber Creek, between Gloucester and Red Bank, N. J., 

 showing the shell, beautifully preserved. It is from the bed usually known 

 as the ' ; Ripley Group," discovered almost simultaneously in Mississippi, by 

 Dr. Spillman, and Prof. Hilgard, the State geologist, and first recognized by 

 me in New Jersey. 



The shell resembles L. Australia nobis (Lilhodomus id., Synopsis Moll, of 

 Cret., Modiola id., Proc. Acad., I860,) but is narrower, posteriorly, and the 

 cardinal margin is more depressed. 



L. a f f i n i s . Tube robust, curved, short. Portion containing the shell 

 broad, grooved at the anterior half of the back, rounded carinate the rest of 

 its length. Opposite face more narrow and deeply grooved. Extremity dis- 

 tinctly trilobate. Shell unknown. From the shape of the tube, it appears 

 related to the preceding species, but the beaks are less prominent in advance, 

 the shell is much more gibbous, the basal margin more emarginate, and the 

 posterior cardinal margin more depressed. 



Length of tube (extending a little beyond the shell) -6 in. Width (in the 

 direction of the length of the shell) -35 in. Transverse width -4 in. 



From the green marl of New Jersey. Exact locality unknown, probably 

 Burlington county. Coll. Acad. 



Although I have only seen the tube of this species, I do not hesitate in 

 describing it. It is shorter, more robust and more distinctly marked by the 

 form of the shell, than that of the preceding species, and is somewhat curved, 

 ft character I have never seen in L. Ripleyanus, after examining more than 

 twenty specimens. The marks on the surface of the tube indicate a much 

 shorter and more robust shell. 



Ctenoides Elein, 1753. 

 Radicla Klein, 1753; Lima Brug., 1792. 



C. denticulicosta . Shell oblique, inflated, thin ; ears small. Surface 

 marked by about twenty-eight angular ribs strongly crenulated on the crest, 

 and occasionally with faint traces of supplementary ribs on their sides. 

 Interspaces between the ribs angular, marked by strong lines of growth, 

 which are more evident at the sides of the shell, at which points the ribs 

 become smaller, and finally disappear, thus leaving about one-sixth of the 

 surface at each side without ribs. Interior marked by grooves corresponding 

 with the ribs on the surface. 



Length, -75 in. Greatest width, -65 in. Depth of valve, "3 in. 



From the Cretaceous of Tennessee. My Coll. and Coll. Acad. From Prof. 

 Safford, the State Geologist of that State. 



This shell resembles C. reticulata nob. {.Lima id. Lyell & Forbes,) but is a 

 little more rounded, especially on the posterior side. It can be distinguished, 

 however, by the ribs being larger, fewer in number, and strongly crenulate, 

 as well as from the fact that, at both the anterior and posterior sides, the ribs 

 disappear for about one-sixth the width of the shell. The umbones are 

 somewhat smaller than in C. reticulata. From C. crenulicosta, it can be dis- 

 tinguished by the shape, being much more elongate, ribs smaller and more 

 numerous, and in the latter species the whole surface is costate. 



Pecten Linn. 



P. tenuitesta. Shell thin, orbicular, flattened ; valves of about equal 



1861.] 



