EOCENE ECHINODERMATA. 147 



The ambulacral areas are narrow, dorsal portions petaloid ; the petals long, rather narrow, 

 nearly closing, the posterior pair slightly longer than the others which are nearly equal in length. 

 The poriferous zones are rather narrow, faintly depressed, outer pores oblong, inner ones round, 

 pairs of pores conjugate. 



The surface of the test, including the interporiferous areas and the ridges between the pairs 

 of pores, is closely set with small imperforate tubercles set in deep scrobicules. Between the 

 tubercles are minute granules. The tubercles increase in size on the under surface except along 

 a narrow band back of the peristome, which is somewhat smooth but dotted with numerous 

 granulations. 



The apical system is excentric anteriorly. There are four genital pores, the anterior pair 

 being nearer together than the posterior; and five perforated radial plates. The madreporite is 

 large, oval and faintly tumid, as are the adjacent portions of the interambulacral areas. 



The peristome is somewhat large, pentagonal, excentric anteriorly, directly beneath the 

 apical system, surrounded by a floscelle of which the bourrelets are rather prominent, granu- 

 lated, and together form a nearly circular ring around the peristome. 



The periproct is elliptical, transverse, supramarginal, at the top of the posterior truncation; 

 beneath a rounded, transverse, somewhat protruding expansion of the test, whose edge is just 

 even with the truncated posterior margin. 



Related forms. — Cassididus carolinensis is closely related to 0. eonradi and resembles it in a 

 number of features, notably in the details of the periproct; but it is to be separated by its less 

 excentric apical system, by its less transverse peristome with the subcircular ring of bourrelets, 

 by being broader, more rounded and less rostrate posteriori}', and by having a more marked 

 concavity around its peristome. 0. carolinensis also resembles C. georgiensis but is to be distin- 

 guished by the concavity around its peristome, its less obtuse and less angular jjosterior margin, 

 and its lower and less oblique posterior truncation. Among European forms C. carolinensis 

 greatly resembles Pygorhynchus maveri De Loriol from the Tertiary of Switzerland (more so than 

 does C. eonradi), but differs in having its periproct higher up on the posterior surface, and in the 

 failure of the expansion of the test over the periproct to protrude noticeably beyond the posterior 

 margin. In a number of features 0. carolinensis is similar to Pygorhynchus grignonensis 

 (Defrance) Agassiz from the Eocene of France, but it can be separated by its more depressed 

 form and the higher relative position of its periproct. 



Localities. — Smith Creek (type), Rocky Point, and Wilmington, N. C. 



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



Collections. — Johns Hopkins University (T 2004) ; U. S. National Museum. 



Cassidulus amygdala Desor. 



Cassididus amygdala Desor, 1858, Synopsis des echinides fossiles, p. lxv. 

 Cassididus amygdala Conrad, 1865', Acad. Nat. Sci. Philadelphia Proc, p. 22. 

 Cassididus amygdala Conrad, 1866, Smithsonian Misc. Coll., vol. 7 (200), p. 22. 



This is a Swiss species described on page 290 of Desor's Synopsis and erroneously listed by 

 Desor in his table of distribution, page lxv, as among the Eocene Echinodermata of America. 

 Conrad, failing to note the error, also listed the form in his catalogue and check list. 



Pygorhynchus ktjgosus Raveiiel. 



Pygorhynchus rugosus Ravenel, 1848, Echinidae, recent and fossil, of South Carolina, p. 4. PI. II, fig?. 7, 8. 

 Pygorhynchus rugosus Ravenel, 1850, Cat. recent and fossil Echinidae, South Carolina, p. 160. 

 Pygorhynchus rugosus Agassiz, 1883, Mus. Comp. Zoology Mem., vol. 10, No. 1, p. 91. 



Ravenel, in 1848, published in an out of the way pamphlet two poi r drawings, unaccom- 

 panied by a description, of a form from the Eocene of South Carolina for which he proposed 

 the name Pygorhynchus rugosus. The species is not entitled to recognition; and the writer 

 has been unable to locate the type or to recognize the form among the material studied. 



