POROCIDARIS PURPURATA. 395 



Porocidaris purpurata 



! Porocidaris purpurata Thoms., 1869, Prel. Rept. Porcup. Exp. 



PI. I'.f. 37-41; PI XXIV. f. 11. 



Other peculiarities, such as the structure of the genital openings, will be 

 shortly described by him in his final Report on the Echinoderms of the 

 Cruise of the Porcupine, and I merely allude to this interesting species, of 

 which the Museum owes him a specimen, to make this Revision as complete 

 as possible, and leave for an Appendix a recapitulation of his description. 



Rockall. 



GONIOCIDARIS. 



Goniocidaris Des., 1846, Agass., C. R. 



The test is frequently higher than broad ; the coronal plates more nu- 

 merous than in the other genera of Cidaridae. Tubercles perforate, with 

 a smooth base. The ambulacra are narrower than in any other genus of the 

 family ; the poriferous zone is almost as broad as the median ambulacral re- 

 gion. The median ambulacral and interambulacral areas are bare ; the su- 

 tures of the plates sunken, and forming, along the vertical sutures near the 

 median line, and along the horizontal sutures, deep zigzag impressions, culmi- 

 nating in a pit at the angle of two plates. In each of these pits, both in 

 the ambulacral and interambulacral zones, are situated large spherical pedi- 

 cellarias with a short stem, a single one frequently filling the whole pit in 

 the interambulacral zone ; they are not so abundant in the ambulacral zone. 

 The spines are cylindrical, the surface covered with thorny spines, pointing 

 irregularly outwards ; flaring, and frequently cupped at the extremity. 



Goniocidaris canaliculata 



! Temnocidaris canaliculata A. Ac, 1863, Bull. M. C. Z. 

 ! Goniocidaris canaliculata A. Ac, 1872, Rev. Ech., Pt. I. 



PI. I'.f. 6-8 ; PI I s . f. 2; PI XXIV. f. 10. 



Abactinal system with slight cuts at angles of coronal plates ; narrow fur- 

 row extending the whole length of the median ambulacral and interambula- 

 cral zones, following the sutures of the plates. Poriferous zone narrow, pores 

 adjoining ; ridge separating pairs of pores prominent. Scrobicular circle 

 well marked, elliptical, surrounded by a prominent row of secondary tubercles, 

 and near the median furrow by a second concentric row of smaller tubercles. 

 Mammary boss small and distinct. Poriferous zone not equal in breadth to the 



