NATURAL SCIENCES Of PHILADELPHIA. 321 



not truncated, nor carinate in the casts, marked by numerous oblique plica- 

 tions ; surface markings unknown. Umbilicus large, dilated, merging by 

 a rounded edge, without any carination, into the external surface. Mouth 

 rounded, widest near the lower extremity. 



Height, 1-5 in. Width of body whorl, 2 in. Length of mouth about 2-3 in. 



This is probably the largest of the NaiicidcR in the American Cretaceous, 

 east of the Mississippi. It exceeds the finest specimens of Gyrodcs (Natica) 

 abyssinis, I have ever seen, in size. 



I am indebted for the only known specimen to my friend, Mr. C. C. Abbott, 

 who has added many rare and valuable specimens to my collection from the 

 N. Jersey marl beds. The specimen is from Mullica Hill, from the shell bed 

 at the top of the hill, known to every collector at that locality. 



From G. crenata, Con., it can be distinguished by the base of the body 

 whorl being broadly rounded. From G. alveata, Con., by the smaller number 

 of whorls to a shell twice the size of the type of that species, by the oblique 

 plications and absence of a carina on the shoulder of the whorl. 



Turbinopsis Con. 



T. depressa. Flattened ; spire low; whorls three, rounded and rather 

 widely separated in casts, indicating a thick shell; slightly channelled at the 

 suture. Mouth elliptical longitudinally, acute below, the lower edge of the 

 whorl very strongly carinate, with the cast of a revolving rib on the lower 

 edge of the inner lip, and on the outer side of the carina are faint depressions 

 at about an eighth of an inch apart, indicating a periodical tooth. These are 

 faint or absent in the small specimens, but quite marked in the largest one 

 before me. Umbilicus patulous, perspective. 



Not very rare in the cretaceous at Crosswicks, N. J., and at the Delaware 

 and Chesapeake Canal. My Collection from Dr. Slack, and Coll. Acad. 



Height (of largest specimen) -85 in. Width of body whorl, 1 in. Length of 

 mouth, -6 in. 



I at first considered this genus as a synonym of Cancellaria. On more care- 

 ful examination, I believe it to be very distinct. It seems to be more nearly 

 related to Ninella of Gray. It has the same general form, but differs in the 

 lower edge of the mouth being acute, with a revolving rib or tooth near the 

 base on the inner lip. 



Cancellaria Alabamensis, nobis, must be placed in this genus. 



The present species can be distinguished by the extremely flattened form, 

 the other species have remarkably high spires, compared with it. 



Trochus Linn.. 



T. M o r t o n i i . Shell conical, spire elevated : whorls four, probably five, 

 increasing very gradually in size obliquely flattened on the sides, and marked 

 by very faint undulations, probably indicating.longitudinal ribs on the shell ; 

 lower edge of whorls angulated, under surface nearly flat ; mouth obliquely 

 subquadrate ; umbilicus ? 



Height, -75 in. Width of body whorl, 1 inj Height of mouth, -4 in. 



From the white cretaceous limestone of Ala.. Coll. Acad. 



There are two specimens in the collection ;: one of them, with the sides of 

 the whorls almost perfectly straight, has the trace of a small revolving rib or 

 tooth near the inner angle of the mouth on the lower lip. It may belong to 

 another species. 



T. Mortonii resembles most nearly T. Marrotianus, d'Orb., in its general form, 

 except that it is a shorter shell proportionally and the umbilicus is closed, or 

 nearly so. The casts also exhibit traces of longitudinal ribs or undulations, 

 which do not exist in the latter species. 



Architectonica Bolt. 

 A. Abbottii. Discoidal, spire low; whorls four, truncated above) 

 1861.] 22 



