MIOCENE ECHINODERMATA. 209 



posterior marginal notches are less pronounced and have one side merging into its more rounded 

 posterior margin. 



Localities. — Dr. Ravenel's plantation, known as "The Grove," on Cooper River, 17 miles 

 from Charleston, and Goose Creek, S. C. ; Alligator Creek, Monroe County, and near Punta Garda, 

 Alligator Creek, Monroe County, Fla. 



Geologic horizon. — Duplin marl, upper Miocene, in South Carolina, Caloosahatchee marl, 

 Pliocene, in Florida. 



Collections. — Academy of Natural Sciences of Philadelphia ( 10S6, A) ; U. S. National Museum 

 ( 164G5S, B; 9970, C) ; American Museum of Natural History; Boston Society of Natural History; 

 Wagner Free Institute of Science. 



Family CLYPEASTRID^I. 



Genus CLYPEASTER Lamarck. 



Clypeaster bowersi Weaver. 



Plate XCVI, figures la-b. 



Clypeaster bowersi Weaver, 1908, California Univ. Dept. Geology Bull., vol. 5, No. 17, pp. 271-272, PI. XXI, fig. 1; 



PL XXII, fig. 1. 

 Clypeaster bowersi Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 701. 



Description. — As the writer has had no opportunity of studying the single specimen 1 of 

 this large Clypeaster that has been discovered the description of Weaver is here given verbatim: 



The test of this form is very large and thick. The largest specimens measured 119 millimeters in diameter. The 

 outline seen from above is circular to elliptical. The margins are swollen and the summit very slightly elevated. 

 On the posterior margin is a faint reentrant angle opposite the anal opening. The petals are broad and nearly closed 

 at the extremity. The median interporiferous zones are broad, while the outer rows of pores converge at the ends 

 so as almost to inclose them. The tuberculation is uniform on both the upper and lower surfaces and the tubercles 

 are of nearly the same size over the whole test. The actinal surface is strongly concave and the actinostome deeply 

 sunken. The ambulacral furrows are very deep and extend from the actinostome to the margin. 



Dimensions. — Maximum width 100 millimeters; maximum length 119 millimeters; maxi- 

 mum thickness 37 millimeters. 



Related forms. — Weaver makes the following remarks on related forms: 



Clypeaster bowersi differs considerably from the other members of this genus on the Pacific coast. It is not far 

 removed from C. breunigei Laube, which occurs in the Eocene in the Lybian Desert of Africa. C. bowersi is nearly 

 twice as large as C. breunigei and is ellipsoidal in outline with thick margins, while the latter is pentagonal and has 

 thin margins. The upper surface of the former is only slightly arched, while the apical system of the latter is conical 

 and then gradually slopes to the margin. They differ also in the character of the petals and in the position of the 

 anal pore. In C. bowersi the petals are broad and the poriferous zones lie nearly parallel. The anus is situated on 

 the actinal surface at a distance from the margin about equal to its diameter. 



Clypeaster bowersishows a close relationship to Diplolhecanthus rosaceus (Lamarck). It differs in that it is much 

 flatter, the superior surface of D. rosaceus being more strongly convex. The actinostome of the former is sunken in a 

 cavity which narrows gradually and is of much greater extent than in D. rosaceus. In D. rosaceus the ambulacral 

 areas are more or less swollen and rise above the general level of the test, while in C. bowersi they are nearly at the 

 same level as the interambulacral areas. The posterior ambulacral petals are the longest and the odd ambulacral 

 petal is the shortest in D. rosaceus. In C. bowersi the odd ambulacral petal is the longest and the remaining four are of 

 equal size. 



Locality. — Colorado Desert (Weaver). 1 



Geologic horizon. — Associated with a fauna presumed to be of Miocene age (Weaver). 1 



Collection. — University of California. 



' Since the above description was written William S. W. Kew has published some additional data relative to C. bowersi based on new 

 material collected by him (California Univ. Dept. Geology Bull., vol. 8, No. 5, p. 50, Pis. IV, V, 1914). He supplements Weaver's description 

 by mentioning that there are faint reentrant angles opposite all the interambulacral areas, that the petals are obovate, that the anterior petal is 

 somewhat raised, and that the periproct is large, depressed, and inframarginal. Kew gives several new localities, all being near Coyote Moun- 

 tain, Carrizo Creek region, California. He also says that C. bowersi occurs at all the localities, in his lower division of the Carrizo Creek forma- 

 tion, the age of which has not yet been definitely determined. Arnold, in 1910 (Willis and Salisbury, Outlines of geologic history, p. 245), 

 regarded the Carrizo Creek beds as equivalent to the Etchegoin formation which is now thought to be upper Miocene and lower Pliocene (?). 



