VaiigJian — RedescripHon of a Coral. 



209 



7a. 



Cotypes of Platytrochus speciosus. 



Fig. 1. General view of specimen, height, 11.25 mm.; Fig. la, costae of 

 the same specimen considerably enlarged; Fig. lb. two systems of septa, 

 showing pali, of the same specimen, slightly diagrammatic; Fig. 2. 

 general view of another specimen, height, 11 mm.; Fig. 2a, caliceof the 

 same, greater diameter, 11 mm. [Figures reproduced through the 

 courtesy of the Director of the U. S. Geological Survey.] 



Locality* — "M. & C. R. R. or Walker's Bank, at Tennessee State Line, 

 Hardeman County, Tennessee." 



Geological Horizon. — "Midway Eocene." 



Cotypes. — No. 87. Department of Geology, Yanderbilt University. 

 Two specimens. 



Remarks. — This species presents an individuality so striking that com- 

 parisons with other species can scarcely be made. I pointed out in de- 

 scribing Trt^cAoc^/rti/ms wooZ»i«m two important differences between the 

 two species, basing my comparison on Gabb and Horn's brief original de- 

 scription, viz: that T. speciosus is three times as large as T. woolmnni and 

 that its calice is much deeper. A third difference is that the former 

 possesses one more cycle of septa than the latter, even when the speci- 

 mens of the two species are of the same size. 



T. speciosus bears considerable external resemblance to occasional large 

 specimens of Paracyathus alternatus Vaughan. The pali and columella 

 are quite different, and even in form there is discernible difference. 

 The ratio of the diameters of the calice to the height of corallum is 

 greater in T. speciosus, i. e. the diameters of the calice in T. speciosus 

 are relatively greater than in P. alternatus. 



*Taken from the label accompanying the specimens. 



