NATURAL SCIENCES OF PHILADELPHIA. 79 



CYCLONEMA CRENULATA, Meek. 



Shell turbinate, subtrocliiform, thin ; spire depressed conical ; 

 volutions four, increasing rather rapidly in size, those of the spire 

 convex but not rounded; last one large, convex on the upper slope 

 to the peripher}^, which is rather narrowlj^ rounded; suture well 

 defined between the upper volutions, and somewhat canaliculate 

 farther down; aperture ovate. Surface ornamented by sharply 

 elevated revolving lines or small ridges, which are beautifully and 

 minutely crenate by the crossing of the fine, very oblique lines of 

 growth ; of these revolving lines from sixteen to eighteen may be 

 counted on the body volution, and six on the next above, while 

 those farther up appear to be quite smooth. 



Length, 0.34 inch ; breadth, 0.32 inch. 



This species seems to be related to G. midtUira, Hall (Fifteenth 

 Report of Regents, p. 48, pi. 5, fig. It), but has a more depressed 

 form, with the volutions of its spire merelj'^ convex instead of 

 rounded, and its body volution narrowly instead of regularly 

 rounded. It also has more revolving lines, which likewise show 

 a delicate crenate character not represented in the figure nor 

 mentioned in the description of C. muUilira. 



In general appearance our shell more nearly resembles Mr. 

 Conrad's original figure of his C. bilix (Journ. Acad., N. S. VII, 

 pi. xvi, fig. 10), but it is less oblique, with more coua'cx volutions, 

 and more numerous revolving lines. 



Locality and position. Same as last. 



ISONEMA HTIMILIS, Meek. 



Shell large and robust, depressed subturbinate, about one- 

 fourth to near one-third wider than high ; spire much depressed : 

 volutions four, increasing rather rapidly in size, the exposed part 

 of those of the spire gently conA'ex ; last one large and regularly 

 rounded, or sometimes very obtusely subangular around the middle 

 of the outer side ; suture well defined, without being properly 

 channelled ; aperture circular a little within, but more or less an- 

 gular above at the immediate edge of the lip, where it is more 

 oval in outline ; outer lip thin, and, in mature specimens, slightly 

 dilated ; inner lip thickened, very distinctly flattened, and slightly 

 spread over the imperforate umbilical region, as well as a little 

 thickened near the top of the aperture. Surface ornamented 

 1871.] 



