NATURAL SCIENCES OF PHILADELPHIA. 83 



than wide, and somewhat angular above, at the connection of its 

 outer lip with the return of the spire, and at the termination of 

 each of the three revolving carinse, as well as very obscurely so a 

 little below the middle of the inner side ; inner lip thin below its 

 connection with the carina passing around the umbilicus, at which 

 point it is very slightl}'' thickened, while above this it seems to 

 be nearly or quite obsolete. Umbilicus rather wide, but shallow, 

 or very rapidly contracting within. Suture well defined, without 

 being in the slightest degree furrowed. Surface only showing 

 very fine lines of growth, which, on the upper flattened space of 

 the volutions, pass obliquely outward and backward, with a very 

 slight curve from the suture to the upper angle or shoulder, below 

 which they pas's nearly straight down the outer flattened area to 

 the second carina, which is as far as they can be traced in the 

 specimen studied. 



Height, 0.81 inch ; breadth, 0.90 inch ; height of aperture, 0.54 

 inch ; breadth of do., 0.46 inch. 



This rather neat shell seems to agree exactly in all of its 

 generic characters with the type of Mr. Salter's genus Troclionema 

 (T. umbilicata, Hall, sp.), excepting in not even showing any 

 tendenc}'' to have its body volution become free at the aperture, 

 nor apparently its peritreme continuous. The first of these cha- 

 racters, however, seems not to be always constant in the typical 

 species of Trochonema ; but the fact that it does generally occur 

 in the same is worthy of note ; while the apparent absence of a 

 continuous peritreme in the shell here under consideration, would 

 certainly seem to be one of more than specific importance. If so, I 

 would suggest for it, at least as a subgeneric designation, the 

 name Trochonemopsis. 



Specificallj^ this shell will be readily distinguished from T. um- 

 bilicata, which it most nearly resembles, not only by its more 

 depressed form, closely contiguous body volution, obsolete inner 

 lip above the middle of the aperture, and more shallow umbilicus, 

 but also by not having its suture channelled and bordered below 

 by a fourth carina around the upper margin of each volution, as 

 in that species. 



Locality and position. Marblehead, Ohio. Corniferous group. 



Note. — In the same matrix with the above-described shell, I have been 

 surprised to notice numerous minute bodies that I can scarcely doubt are 



1871.] 



