FROM THE TERTIARY OF VIRGINIA. 269 



and carina at right angles. The carina is placed immediately below the middle of the 

 whorls, and, in some specimens, between it and the lower suture is another smaller one. 

 When this latter is not present, it is replaced by a stria. Between the carina and upper 

 suture there are generally two stri, which vary in size. Those on the base are much 

 smaller than those on the whorls. The sutures are small and triangular. 



This shell is unusually short and thick for a Cerithium, and its effuse mouth has 

 hardly the character of the canal of that genus. 



C. D^DALEUM, PL. 37. FIG. 91. 



C. testa subulatd, tenui, imperforatd, costatd, striatd; spird attenuala, sub-ovatd, mamillatd, ad apicem Icevi et 

 politu; suturis linearibus, parvis; anfraclibus septem, planulatis; costis longitudinalibus, crebris, l&vibus, planulatis; 

 striis transversis, crebris, profundis; ultimo anfractu rotundato; basi striatd, polita; aperturd arctatd, sub-quadratd } 

 superne angulatd, inferne effusd; labro acuto. 



Shell subulate, thin, imperforate, costate, striate; spire attenuate, sub-ovate, maraillate, smooth and polished near 

 the apex; sutures small, linear; whorls seven, flattened; striae transverse, numerous, deep; costse longitudinal, nume- 

 rous, smooth, flattened ; last whorl rounded; base striate, polished, mouth narrow, sub-quadrate; angulate above, effuse 

 below; outer lip acute. 



Length .15. Breadth .05 of an inch. 



Remarks. The sculpture of this shell is not unlike that of the Pasithea subula, herein 

 described. 



With this shell, as with the preceding, I feel in some doubt as to the genus to which 

 it properly belongs. 



C. MONILIFERUM, PL. 37. FIG. 92. 



C. testa subulatd, sinistrali, crassd, imperforatd, costatd; spird attenuatd, conic&j suturis minimis; anfractibus 

 decem. plants; costis tribus, transversis, noduliferis, duabus extremis magnis, und media parviore; anfractu ultimo 

 rotundato; basi costis tribus, lavibus, transversis; aperturd elongato-quadratd; columelld Itevi. polita; canale profundo, 

 brevi. 



Shell subulate, sinistral, thick, imperforate, costate; spire attenuate, conical; sutures very small; whorls ten, flat; 

 costae three, transverse, noduliferous, two extreme ones large, the middle one smaller; last whorl rounded; base with 

 three transverse, smooth ribs; mouth elongately quadrate; columella smooth, polished; canal deep, short. 



Length .22. Breadth .09 of an inch. 



Remarks. The middle costa is smaller than the two outer ones; it gradually decreases 

 on the upper whorls, and finally becomes obsolete near the apex. The sutures are very 

 small, and the whorls perfectly flat, so that it is difficult to determine their number. 



This shell approaches the C. nigrocinctum, Adams, a recent species from our coast, 

 but may be distinguished by its greater proportionate length, flatness of the whorls, and 

 the difference between the size of the ribs. It is also allied to the C. perversum, another 

 recent shell, but it is much smaller, and the ribs are strictly noduliferous, while in the 

 C. perversum, they intersect longitudinal sulci. The three smooth basal costa? consti- 

 tute another character peculiar, I believe, to this shell. 



GENUS PLEUROTOMA. 

 P. LUNATUM, PL. 37. FIG. 93. 



P. testa elongato-fusiformi, crassd, glabrd, nitente, imperforatd, costatd; spird attenuala, mamillatd, ad apicem 

 Itevi; suturis fiexuosis, minimis; anfractibus decem, media angulatis, inferne convexis et costatis, superne concavis et 

 VOL. IX. 71 



