INVERTEBRATES. 353 



about every fourth or fifth one of which is considerably larger 

 and more prominent than the others near the suture above ; 

 and they all curve obliquely backwards as they approach the 

 angle supporting the spiral band. Length, 0.55 inch; breadth, 

 0.52 inch ; apical angle regular, divergence 82 ° ; breadth of 

 spiral band not more than about 0.03 inch. 



This very neat, elegantly ornamented species, will be readily distinguished 

 from any of those yet known in our Coal Measures (resembling it in form), by 

 its peculiar prominent, neatly crenulated spiral band, and its extremely fine, 

 closely arranged lines of growth. 



Locality and position : Same as preceding. 



Pleurotomaria scitula, M. and W. 



PI; 28, figs. 9a, 9b, 9c, 9d. 



Pleurotomaria scitula, Meek and Worthen, Oct., 1860. Proceedings Acad. Nat. Sci., 

 Philad., p. 461. 



Shell small, trochiform, length and breadth nearly equal; 

 spire depressed-conical; volutions six, a little convex, last one 

 prominent and narrowly rounded, or subangular on the peri- 

 phery, slightly convex below; suture somewhat canaliculate; 

 aperture subcircular, approaching a subquadrate form; umbili- 

 cal region impressed, but not distinctly perforated; spiral band 

 of moderate breadth, concave, and located a little above the 

 periphery of the body whorl, but passing around, slightly below 

 the middle of the other volutions. Surface ornamented by 

 from about seventeen to twenty-two revolving lines, only three 

 or four of which occupy that part of the body whorl above the 

 band, where they are larger and more widely separated than 

 below; distinct, but much smaller, regularly arranged, thread- 

 like lines, mark the volutions transversely. Length and 

 oreadth each about 0.22 inch; apical angle convex, diver- 

 gence, 79°. 



45 Sbpt. 25, 1S66. 



