194 Trans, Acad. Sci. of St. Louis. 



*' This Gyroceras is of unusually large dimensions, — about 

 fifteen inches in diameter, and nearly three feet along the 

 dorsal circumference of a single coil. It occurs in the oolitic 

 bed, at the top of member a, of the Lower Series of Carbon- 

 iferous Limestones, under the encrinital beds of the quarries 

 at Burlington, Iowa." 



Remarks. This species has not been observed by the 

 writer. In connection with its original description, its strati- 

 graphic position at Burlington was so definitely stated that 

 there can be no doubt of its being a member of the fauna 

 under discussion. A tracing of the outlines of the original 

 drawing is presented on plate XVIII, but according to the 

 dimensions given for the species, this drawing must be less 

 than one-third natural size, although no statement to that 

 effect is made in the explanation of the original plate. 



V. THE FAUNA OF BED NO. 7. 



COEIiENTERATA. 



Leptopora typa Win. 



PI. XX. f. 19. 



Original description. ** Polypary subcircular in outline^ 

 and slightly convex on the general surface; composed (in the 

 specimens examined) of about 25-30 rather large cells of 

 which the internal ones are hexagonal, and the peripheral 

 rounded exteriorly ; margins of cups strongly elevated ; radial 

 lamellae about 20." 



*' Diameter of mass 18 mm., diameter of cells about 3| mm., 

 and their depth about 1| mm." 



Remarks, The type specimens of this species in the 

 University of Michigan collection are two in number, one 

 being a cast of the surface of a corallum and another less 

 perfect colony shows several corallites in which the substance 

 of the coral has been preserved. The specimen here illus- 

 trated is the cast and in it the bounding rims of the corallites 

 are of course represented by grooves instead of elevations. 

 In the specimen retaining the coral substance each corallite 



