320 PROCEEDINGS OF THE ACADEMY OP 



From the same formation, in N. J., as the preceding species of Acteon. My 

 Coll., and Coll. Acad. 



Closely related in general form to iV". abyssinis. The measurements are 

 somewhat different. Dr. Morton's type measures, Height, 1 in. Width of 

 body whorl, 1-30 in. Length of mouth, 9 in. The most obvious difference is 

 in the shape of the lower edge of the whorls. In N. abyssinis only known from 

 casts, it is regularly rounded. In this species it is carinate. The species 

 may prove to belong to the genus Gyrodes Con., on account of the wide um- 

 bilicus, apparently without a callus, and the flattened top of the whorl. 



Lunatia Gray. 



? L. altispira. Elevated subglobose. Spire rather high ; whorls four, 

 rounded, abruptly truncated or concave above. Body whorl gibbous. Mouth 

 broad, rounded. Umbilicus (in casts) small, perforated rather deeply. No 

 markings on the casts. 



Length. 8 in. Width of body whorl, *7 in. Length of mouth, -6 in. 



Found with the preceding. My Coll., Coll. Acad. 



Approaches most nearly to L. rectilabrum = ? L. concinna H. & M., but can 

 be at once distinguished by the abruptly truncated superior edge of the whorl. 

 This character relates it to, if it will not place it in the following genus. 



Gyrodes Con. 



? G. obtusivolva. Shell subglobose ; spire somewhat elevated ; whorls 

 three, abruptly truncated above, where they are flat or concave with the angle 

 acute. Body whorl gibbous, sloping below. Mouth biangular above, broadly 

 rounded below. Umbilicus narrow, deeply perforate in casts. Surface 

 marked by close irregular oblique striae. 



My Coll., from Mr. Abbott, n. g. 



Length, -8 in. Width of body whorl, -8 in. Length of mouth, -55 in. 



Approaches in form the preceding species, but is a more robust shell, the 

 truncations of the body whorl is much broader and more abrupt, and the sur- 

 face is distinctly striate by lines of growth. The umbilicus appears broader, 

 but this may be merely an individual character. 



The genus Gyrodes will probably have to be extended to receive a number 

 of forms, having all the other characters as described by Mr. Conrad, but 

 with a narrow umbilicus. 



Unfortunately, we are unable to determine positively, whether or not there 

 was a callus in the umbilical cavity of this species. Could we determine that 

 point, we might be able to settle the bounds of the genus. 



G. Spi lima nii. Shell wide, spire low; whorls three, oblique on the 

 sides, truncated above. The truncation is at times flat, sometimes concave^ 

 angle generally acute. Mouth biangular above, obliquely expanded below. 

 Umbilicus broad, open, margin subcarinate. 



Height, -7 in. Width of body whorl, -85 in. Length of mouth, -55 in. 



Two specimens (casts) from the cretaceous limestone of Mississippi, in the 

 collection of the Academy, presented by Dr. Spillman. Closely related to 

 Gyrodes (Natica) petrosa, which is found in the same locality, but differs in 

 the outer edge of the mouth being much less obliquely expanded, the surface 

 of the whorls being much more nearly parallel with the longitudinal axis of 

 the shell than in that species. The umbilicus is probably larger, but it 

 expands at a much smaller angle. G. petrosa has much the outline of Siyare- 

 tus. This is nearer the usual form of the true Naticas. 



G. Abbotti. Shell subglobose, spire low, hardly elevated above the 

 upper edge of the body whorl. Whorls three? (partly covered in the middle 

 by matrix) rapidly increasing in size. Section of body whorl (= curve of the 

 outer lip) nearly semicircular. Upper surface of the whorls flattened, but 



[Oct. 



