May, U)17] 



Silurian Fossils from Ohio 



237 



Compared with typical CaUocystites jewetti, from the Roch- 

 ester shale of New York and Ontario, the theca is slightly longer 

 and narrower, being less inflated at mid-length. Moreover, the 

 halves of the pectinirhomb on plates 1 and 5 are much more 

 widely separated from each other. It also is probable that if 

 perfect specimens were at hand that other differences might be 

 noted but the Cedarville specimen evidently is closely related 

 to the Rochester shale species. 



Fig. 2. Plate diagram of CaUocystites jewetti-elongata. Poorly preserved 

 outlines indicated by broken lines. The suture lines between plates 13, 19 and 

 24 are unknown. 



At the eastern Mills quarry, southeast of Springfield, Ohio, 

 another fragment of CaUocystites (Fig. 3) was found in the 

 Cedarville dolomite which evidently also is closely related to 

 CaUocystites jewetti. The specimen is a fragment of a cast of 

 the exterior of the theca and shows the characteristic deeply and 

 coarsely pitted surface; the sharply elevated margin and 

 elliptical outline of that half of the pectinirhomb which is 

 located on plate 14, and the less strongly elevated margin and 

 more triangular outline of that half which is on plate 15. 

 Plates 9 and 10 are pentangular, 9 with the angle directed 

 downward, 10 with the angle directed upward. The smooth 

 depressed linear area left by the falling off of the ambulacrum 

 is unbranched, and its median part passes somewhat diag- 

 onally toward the left of the suture hne between plates 9 and 10. 

 Parts of plates 4, 16, 19, 20, and 21, also are present. There is 

 a possibility of this cast of the exterior of the theca being 

 identical specifically with the cast of the interior from the 

 Cedarville dolomite, at Yellow Springs, described in the 

 preceding lines. 



