APPENDIX TO DECADE V. 



3 



granulated miliary furrow; interambulacral tubercles 9, 10, with small 

 laterals on the under surface ; ambulacral tubercles 8, 8, with large con- 

 fluent areolae at the circumference. Pores in single file. 



The test of this species is more highly ornamented than any of the 



preceding forms, but the upper surface appears nearly plain unless 



examined with a glass. 



Locality. — Common in the hard gritty Chalk of Dover, and occa- 

 sionally found in the Chalk with flints in Sussex. 



8. C. difficile, Ag., Cat. Syst., p. 11. Diadema rotatum, and D. M^Coyi, 

 Forbes, in Morris's Cat., 2nd ed., p. 76, 77. Diadema rotulare, M'Coy (not 

 Ag.). Glyphocyphus difficilis, Desor, Syn., p. 104. 



Body small, lat. 7, alt. 3 lines, convex above, slightly concave beneath ; 

 mouth circular, lat. 2J- lines ; apical disk equal to the oral opening, flat, finelj- 

 granulated ; ocular plates rather large, perforated close to the ambulacral 

 margin ; genital plates perforated (with a sur-anal plate in the centre ?), 

 and the madreporiform body on the right anterior plate ; poriferous 

 avenues nearly straight, distinct, with the pairs of pores in single series ; 

 tubercles prominent, quite smooth unless weathered, placed on crenulated 

 bosses ; ambulacra narrow, straight, with remote alternate tubercles ir- 

 regularly developed, 3, 8, or 7, 8 ; interambulacrals in two straight rows 

 of 8, 9, surrounded by small strongly radiated areolas, and divided by deep 

 sutural notches. 



Small specimens, measuring 4 or 5 lines, are abundant, and usually 

 overlooked as the young of the Diademas, but may be readily dis- 

 tinguished by the sutural notches. The more convex examples 

 agree with the published mould of M. Agassiz's type specimen of 

 C. difficile, but there is nothing in the description of C. sulcatum^ 

 Ag., to distinguish it from the same urchin. An unusually large 

 specimen (in the cabinet of Mr. Sloper, of Devizes) measures 9 lines 

 across and 4J in height ; both rows of ambulacral tubercles are 

 well developed, and the miliary granules form a prominent frame- 

 work to the tubercles. Two specimens have occurred with the 

 apical disk, one of which is in the Brit. Mus., and the other in 

 Mr. Cunnington's Collection. 



M. Desor refers this urchin to D'Archiac's Glyphocyphus (which was 

 founded on the Temnopleurus pulchellus of Sorignet, Echinopsis 

 pusilla, Koemer, and incorrectly described as having the tubercles 

 imperforate, and bosses not crenulate), but the structure of the 

 apical disk is altogether different. 



Locality. — Chalk Marl, Dover (Mus. Brit, and Tennant). Upper 

 Green Sand, Warminster. 



9. C. mespilia, n. sp. 



Body small, circular, inflated or depressed, convex above and below, 

 with sub-equal apertures ; lat. 5, alt. 3 lines ; poriferous avenues quite 



