

May, 1909. New Echinoids — Slocom. 7 



other parts of the test are complete. In general form this species 

 resembles C. cequoreus, but it is not so high in proportion to its length, 

 the periproct is somewhat higher, the pores in the outer rows 

 of the petaloid portions are slitlike instead of round and the 

 expansions of the phyllodes are wider. C. intermedins resembles 

 C. micrococcus in the slitlike pores of the outer rows of the petaloid 

 areas and in the expansion of the phyllodes, but the position of the 

 pores in these expansions is more like those of C. cequoreus. The 

 position of the periproct is midway between that of C. micrococcus 

 and C. cequoreus, the size and shape of the test is quite unlike C. 

 micrococcus and the extension of the longitudinal median band in 

 front of the peristome on the ventral surface does not appear, from 

 the description and figures, to occur in either of the other species. 

 The name adopted for this species refers to the characters inter- 

 mediate between C. cequoreus and C. micrococcus which the species 

 exhibits. 



Locality: Ripley Group near the southern edge of the village of 

 Pontotoc, Mississippi. 



Cassidulus hemisphericus sp. nov. Plate I, Figs. 7-9. 



Test subhemispherical with its transverse diameter somewhat 

 shorter than the longitudinal, sides arcuate, margins angular, ventral 

 surface flat or nearly so. Ambulacral areas wide, subpetaloid on the 

 top of the dorsal surface, not closed distally, petals subequal in 

 length, extending about half way from the apex to the margin, 

 slightly convex; from the distal end of the petals the ambulacral 

 areas are continued as a band which gradually increases in width 

 from the petal to the margin, most of the way being wider than the 

 petal. On the ventral surface the bands slightly narrow to the 

 floscelle. The floscelle is not well preserved in the type specimen, but 

 enough is preserved to determine that the bourrelets are prominent 

 and that the phyllodes are in grooves. The apical system is central 

 but the form of the various plates of which it is composed cannot be 

 determined. The interambulacral areas are about equal in size. 

 They form an acute angle near the apex and rapidly expand to the 

 margin, the plates being comparatively large. All the plates of the 

 dorsal surface, with the exception of those of the petals, are marked 

 by prominent lines subparallel to the edge of the plates. These lines 

 are farther apart on the lateral edges than on the proximal and distal 

 edges. They appear to be lines of growth. The middle portion of 

 the plates within this series of lines is inflated, so that in the small 

 plates of the interambulacral areas, near the apex, the centers of 



