309 



yond the aperture of the shell, and attached only at its constricted 

 base. Two long cirri arise fi'oni the body on the right side, near 

 the junction of the mantle ; these protrude like vibracula from 

 the superior angle of the aperture, when the animal is in motion. 

 Operculum thin, flexible, and pellucid. 



The shell is thin, discoidal, convex above, concave and um- 

 bilicated below; the edge thin and sharp. Whorls three in 

 number, rapidly enlarging. Surface smooth and glossy, indis- 

 tinctly striated with lines of growth. Lip not thickened. Diam- 

 eter one eighth of an inch. 



Hab. Harbor of Charleston, S. C. ; parasitic on Acoetes 

 lupina. 



Dr. B. J. Jeffries exhibited the Atlas and Axis of a 

 man about fifty-five years of age, and very muscular. 

 The Odontoid Process was not united with the Axis. 



Mr. Edward Daniels, State Geologist of Wisconsin, 

 and a corresponding member of the Society, presented a 

 number of geological specimens from that State, and 

 remarked as follows : — 



Occurring throughout an extensive district of Eastern Wis- 

 consin and Northern Illinois, is a rock of Upper Silurian Age, 

 clearly corresponding to the Clinton or Niagara groups of the 

 New York Reports. In numerous localities, this rock contains 

 cavities and thin seams filled with solid bitumen, which is fre- 

 quently found in the digging of wells and cellars, and is commonly 

 called coal. Near Chicago, is an outcrop of this rock, in which 

 bitumen is very extensively found, in fluid form at ordinary tem- 

 peratures, as well as in the solid state. The cavities sometimes 

 contain half a pint. The rock is an Encrinal Limestone, the en- 

 crinal forms being quite distinct in the northernmost portions of 

 the district. From the walls of a church erected of this stone 

 the bitumen has exuded and run down in streams, giving the 

 building the appearance of some of the ancient ruins of Europe. 

 The scale of bitumen peels ofl", however, after some time. Quar- 

 ries have been opened in the limestone to the depth of fifteen 



