C. D. Wdlcott— Paleozoic Pteropods. 19 



sides, and fine papillae, arranged in lines that cross each other 

 at right angles, on some shells; on others, the papillae are 

 arranged in lines parallel to the lines of growth and without 

 reference to the order of those in the adjoining lines; the inte- 

 rior surface is covered with a fretted work brought out by de- 

 pressed, irregular, inosculating lines ; this surface varies in 

 force and character, and some shells are almost smooth inside ; 

 a narrow, smooth space extends all around the margin of the 

 inside of the aperture. 



The associated operculas vary in form and outline ; the shell 

 is calcareous, concavo-convex, rising to a blunt point more 

 towards one end than the other ; from this point long, narrow, 

 radiating undulations extend to the margin, and it is the center 

 of the concentric undulations of growth. Surface with concen- 

 tric and radiating undulations, fine, inosculating lines, sub- 

 parallel to the concentric undulations, and fine papillae on the 

 spaces between the inosculating lines; interior surface convex, 

 smooth or showing the undulations of the outer surface; at 

 the center, corresponding to the apex of the outer surface, a 

 small, round scar appears to be indicated on some specimens. 



The only form known to me that corresponds in any way to 

 this, is that figured by Bichwald (Leth. Boss., pi. xl, fig. 19, a, 

 b, c), as Hyolithes paradoxus, which appears to be the cast of a 

 portion of the outer chamber and one of the conical inner 

 chambers ; it may be only a superficial resemblance. 



Formation and locality. — Cambrian. Limestone resting on 

 Potsdam sandstone, one mile northwest of Saratoga Springs, 

 N..Y. 



The species is associated with Oryptozoan proliferum Hall 

 (Thirty-sixth Ann. Eep. K Y. State Mus. Nat. Hist., despt. of 

 pi. vi, 1884), Platyceras minutissima W., Ptychoparia (L.) cal- 

 cifera W., Dicellocephalus Hartti W., and Ptychaspis speciosus W. 

 (Thirty-second Ann. Eep. K Y. State Mus. Nat. Hist.) 



Note on Hyolithes (Camarotheca) Emmonsi Ford. — When study- 

 ing the species of Hyolithes from the Georgian Group, I found 

 that the shell of H. Emmonsi, of Ford, was formed of three or 

 more distinct layers : first, a thin outer layer with rather strong 

 even strias that cross the flattened ventral face nearly direct, and 

 arch forward on the dorsal face, the flattened side, in this spe- 

 cies, being the ventral face and not the dorsal, as in most spe- 

 cies ; the second layer appears to be of a smooth, even charac- 

 ter, much like a filling between the outer and inner shell ; the 

 inner shell is thin and concentrically striated in a slightly dif- 

 ferent manner from the outer shell ; a fourth layer appears to 

 exist in one example, but it is too obscure for study. 



Another character observed is one that, as far as I know, has 



