NEW ECHINOIDS FROM THE RIPLEY GROUP OF MISSISSIPPI. 



BY ARTHUR WARE SLOCOM 



The specimens upon which this paper is based were collected by 

 the writer in the spring of 1908, during a trip made to Mississippi for 

 the purpose of obtaining a representative series of fossils from the 

 well-known Cretaceous and Tertiary deposits of that state. 



The Ripley formation of Mississippi, from which the specimens 

 here described were obtained, extends southward from Tennessee, on 

 the border of which state it has a width of about 10 miles. In the 

 southern part of Tippah County it widens out to about 1 5 miles and 

 from thence gradually narrows as it passes south through Union 

 and Pontotoc Counties until near Houston in Chickasaw County it 

 disappears altogether. For the most part this formation occupies 

 the highlands and is locally known as the Pontotoc Ridge. Over a 

 large part of this region the Ripley is overlain by red sands and clay 

 of the Lafayette and Wilcox groups, so that the Ripley beds are often 

 found in the gullies and along the streams and are recognized on 

 account of their light color. They are locally called "white gullies." 



At Pontotoc, Mississippi, three localities were visited, viz: (1) 

 the Patterson farm about three miles southeast of town; (2) the 

 bluffs on either side of One Mile Run, about a mile south of town on 

 the Houston road; and (3) the roadside near the southern edge of the 

 village. These two latter outcrops are similar in position, compara- 

 tively near together and will be considered in this paper as one locality. 

 The outcrop on the Patterson farm lies somewhat higher than the 

 other two and is probably higher geologically. At all these localities 

 well preserved echinoids were found. About 200 specimens were 

 collected which proved, on examination, to represent six species, 

 four of which are new and are here described. 



CLASSIFICATION AND TERMINOLOGY. 



The classification here used is that prepared by P. M. Duncan,* 

 and given in the English edition of Zittel's Text Book of Paleontology. 



* P. M. Duncan 1889, Revision of the Genera and Great Groups of the 

 Echinoidea, Jour. Linnean Soc. Vol. XXIII. 



Field Mus. Nat. Hist. Geol. Ser. Vol. IV, No. 1. 



