EOCENE ECHINODEBMATA. 145 



The anibulacral areas are obscure on the specimens studied; but are apparently narrow 

 with petaloid dorsal portions. The narrow poriferous zones show an outer row of slitlike 

 pores and an inner row of round pores. The other details can not be made out. The apical 

 system is excentric anteriorly; its details are not discernible. 



The peristome is small, pentagonal, slightly elongate longitudinally, anteriorly excentric, 

 beneath the apical system, with a well-defined floscelle having prominent bourrelets and rather 

 extensive rounded phyllodes. 



The periproct is small, elliptical, transverse, situated rather high above the posterior 

 margin in an indentation in the test. 



The surface of the test is covered with numerous small tubercles, with scrobicules, larger 

 on the under surface. Between the peristome and the posterior border there extends a wide 

 elliptical, cribriform area. 



Related forms. — This form is most closely related to Cassidulus patelliformis (Bouve) 

 from which it is readily distinguished by its smaller size, more depressed form, the higher 

 position of its periproct, and the greater relative elevation of the upper surface between the 

 periproct and the apical system. It also resembles Cassidulus raveneli but is very much smaller, 

 and its periproct has a less conspicuous overhanging rostrum in a shallower depression. In 

 several respects it resembles Ehynchopygus pygmxus Duncan and Sladen from the Tertiary of 

 India, but it is more depressed and much narrower posteriorly. 



Locality. — Baker County, Ga. 



Geologic horizon. — Probably upper Eocene. May be lower Oligocene. 



Collection. — Boston Society of Natural History (1557a, A; 1557b, B). , :.. ■ 



Cassidulus (Pygorhynchtjs) conradi Conrad. 



Plate LXVII, figures la-f. 



Catopygus conradi Couper MSS., fid. Conrad. 



Catopygus conradi Conrad, 1850, Acad. Nat. Sci. Philadelphia Jour., 2d ser., vol. 2, p. 39, PI. I, fig. 9. 



Cassidulus conradi Conrad, 1865, Acad. Nat. Sci. Philadelphia Proc, p. 75. , . v . 



Cassidulus conradi Conrad, 1866, Smithsonian Misc. Coll., vol. 7 (200), p. 22. 



Catopygus conradi Agassiz, 1883, Mus. Comp. Zoology Mem., vol. 10, No. 1, p. 90. 



Cassidulus conradi Stefanini, 1911, Soc. geol. italiana Boll., vol. 30, p. 700. 



Determinative characters. — Test ovate in marginal outline, broad anteriorly, narrowin°- 

 abruptly posteriorly; sides and anterior end somewhat flattened, posterior end truncated; 

 upper surface convex, depressed, flattened on top ; under surface flattened, slightly concave 

 around the peristome; apex usually forward of the center. Ambulacra! areas narrow. Apical 

 system very excentric anteriorly. Peristome excentric anteriorly, less so than the apical system 

 pentagonal, transversely elongate, with a floscelle. Periproct elliptical, transverse, supra- 

 marginal; beneath an overhanging expansion of the test, whose edge is even with the posterior 

 margin. 



Dimensions. — Length 41 millimeters; width 35 millimeters; height 23 millimeters. 



Description. — This species was first figured in 1850 by Conrad, who also gave a good descrip- 

 tion of the form. He, however, credits the species to a manuscript description by J. Hamilton 

 Couper and says that the name given was adopted at the particular request of Mr. Couper. 

 The test is ovate in marginal outline, broad anteriorly, narrowing abruptly posteriorly; margin 

 somewhat flattened anteriorly, more so on the sides which are nearly vertical at the ambitus 

 but round over the edges to the upper and lower surfaces, obliquely truncated posteriorly and 

 truncated vertically at the posterior end. The upper surface is convex, depressed, flattened 

 on top, and in the form of a low, rounded ridge above the periproct; undersurface flattened, 

 slightly concave around the peristome and slightly convex posteriorly. The lower edge at the 

 posterior end is somewhat prominent, angular and slightly rostrate. The apex is usually 

 forward of the center, when it is coincident with the apical system; but even then it is only 

 slightly higher than the surface of the posterior interambulacrum, and in some forms the upper 

 surface is so depressed anteriorly as to make the apex excentric posteriorly. 



