150 MESOZOIC AND CENOZOIC ECHINODERMATA OF THE UNITED STATES. 



shape and closer together; on the upper surface they are more scattered and in granulated rings 

 between which the surface is dotted with numerous small pits. 



The apical system is excentric anteriorly and consists of four perforated basal plates, the 

 anterior genital pores being closer together than the posterior, five small perforated radial plates, 

 and a large, central, granulated, faintly tumid madreporite. 



The peristome is rather large, regularly elliptical, transverse, excentric anteriorly, though 

 slightly less so than the apical system, surrounded by an inconspicuous floscelle with straight 

 feeble phyllodes and faintly denned, slightly tumid bourrelets. 



The periproct is rather large, irregularly elliptical, the upper edge being less convex than the 

 lower edge and constituting the extreme protruding posterior end of the test, inframarginal, 

 beneath the overhanging rounded ridge of the posterior upper surface and level with the down- 

 wardly oblique truncation of the posterior margin. 



Related forms. — Echinolampas appendiculatus is not closely allied to any other American 

 species. It is easity distinguished from E. aldrichi, the only other representative of the genus 

 yet reported from the United States. It resembles rather closely Echinolampas francei Desor 

 from the Eocene of France but differs in being relatively broader and in having a more regularly 

 elliptical peristome. 



Localities. — Newbern, (Emmons), Rocky Point (figured form), Smith Creek, and Wil- 

 mington, N. C. 



Geologic horizon. — Castle Hayiie limestone, upper Eocene or Oligocene. 



Collections. — Williams College; U. S. National Museum (138017) ; Johns Hopkins University. 



Suborder STERNATA. 

 Family SPATANGIDJE. 



Genus HEMIPATAGTJS Desor. 



Hejiipatagtts argutus Clark, n. sp. 

 Plate LXIX, figures la-d. 



Determinative characters. — Test small, cordiform, depressed, highest just back of posterior 

 truncation, nearly as broad as long, nearly flat below, with broad anterior sulcus. Ambulacra 

 nearly flush, with slightly depressed poriferous avenues. Interambulacra are broad, the paired 

 area with several widely scattered rather large, crenulate and perforate tubercles, with deep 

 areolas giving the surface an irregularly pitted appearance. The lower flat surface has many 

 tubercles of similar character especially on the sides near the ambitus. The tubercles are much 

 worn on both the upper and lower surfaces of the specimen. 



Description. — The single specimen of this very beautiful form has a small test, cordiform in 

 outline, somewhat depressed and nearly as broad as long. The upper surf ace is flattened ante- 

 riorly and elevated posteriorly just back of the posterior truncation. A broad anterior sulcus 

 crosses the ambitus. The lower surface is nearly flat. 



The ambulacra are nearly flush, the poriferous avenues being slightly depressed, subpetal- 

 oidal, the anterior pair being shorter than the posterior. 



The interambulacra are broad, the paired areas with several widely scattered rather large, 

 crenulated and perforate tubercles, with deep areolas giving the surface an irregularly pitted 

 appearance. The lower flat surface has many tubercles of similar character especially on the 

 sides near the ambitus. The tubercles are much worn on both the upper and lower surfaces of 

 the specimen. 



The apical system is indistinct. The peristome is large and oval in outline. The periproct 

 is' large and supramarginal in position. 



Related forms. — The species is similar in certain features to H. subrostratus but is wider 

 anteriorly, has a more cordate form, and is higher posteriorly. 



Locality. — Enterprise, Clarke County, Miss. 



Geologic horizon. — Claiborne group, middle Eocene. 



Collection. — U. S. National Museum (141107). 



