OF WESTERN SIND. 51 



OrtZer ECHINOIDEA EXOCYCLICA. 



Suborder GNATHOSTOMATA. 



Family CONOCLYPEID^. 



Genus CONOCLYPEUS, Agassiz, 1840 (amended). 



Large Urchins, more or less oval or elliptical in marginal outline, conical, vaulted 

 swollen or subconical above, rather flat actinally, and with a thick test. Apical system 

 button-shaped and projecting ; ocular plates very small. Ambulacra very long, straight, 

 not tending to close ; poriferous zones broad, conjugate ; grooves well developed ; inter- 

 poriferous zone large. Peristome central, with well developed tumid bourrelets, and 

 without a phyllode. Jaws exist, and auricles also. Periproct inframarginal or mar- 

 ginal, oval and longitudinal. Ornamentation small, very equal, of sunken scrobicules 

 surrounding small tubercles, with a mamelon which is perforate and crenulate, and 

 separated by a raised surface minutely granular. 



1. CoiirocLYPEUS SiNDBNSis, sp. nov. Plate XII, Figs. 1-4. 



The test is very thick, elliptical in marginal outline, subconical, broader than high, 

 longer than broad, more tumid anteriorly than posteriorly (above the swollen ambitus), 

 and sloping more suddenly anteriorly than posteriorly. The transverse section in a line 

 with the apical system, which is excentric in front, is nearly hemispherical above. In 

 the longitudinal section, the posterior slope from the apical system is at first rather 

 sharply impressed, then curved outward somewhat tumidly at about two thirds the 

 distance from the apex to the posterior extremity, and thence slopes down rather rapidly 

 to the margin. The actinal surface is slightly tumid, and slopes to the margin and 

 to the central peristome. Apical system defective, but was small. 



The ambulacra are long and unequal. The odd and the anterior pair are straight ; 

 and the posterior pair, which are the longest, are gracefully curved, being bowed out 

 laterally at their upper third conformably with the incurved or impressed portion of the 

 odd interradium. They do not come very close to the margin, and are widely open 

 at the extremity. 



The poriferous zones are broad ; the pairs of pores are numerous, the grooves 

 between them well pronounced, and the raised intermediate ridges have one row of well- 

 developed granules. In the anterior odd ambulacrum the poriferous zone is broader 

 than the interporiferous area, except in the actinal third, where this last region is 

 slightly the broadest. But in the posterior ambulacra, at the lower end of the upper 

 third the interporiferous zone is equal in breadth to one of the poriferous zones. The 

 inner pore is larger than the outer. 



At the actinal termination of the ambulacra, and above the margin, the poriferous 



