GENERA AND GEOTJPS OF THE ECHENOIDEA. 123 



G-enus Echinosteephus, A. Agassiz, 1863, Bull. Mus. Comp. 

 Zool. vol. i. p. 20 ; 1873, Bevision, p. 457. Steivart, 1880, 

 Journ. Boy. Micr. Soc. vol. iii. p. 909. De Loriol, 1883, 

 Ech. de Vile Maurice, p. 31. 



Test moderate in size, circular or pentagonal in tumid ambital 

 outline, turban-shaped, but depressed above and widest there, 

 flat below. Plates rather numerous, high actinally, low and 

 broad dorsally. 



Apical system circular, large ; the ring narrow ; basal plates 

 equal and large ; the radial plates small and wedged in between 

 the basals, but excluded ; periproct polygonal, and with large 

 and small plates. 



Ambulacra with rather broad poriferous zones ; pores in arcs 

 of three or four pairs ; interporiferous area with two rows of 

 vertically placed, imperforate and plain, primary tubercles flanked 

 by a vertical row of smaller tubercles placed near the pori- 

 ferous zone ; median area with secondary tubercles and miliaries, 

 arranged more or less around the primary tubercles. 



Interradia broad, with sis to ten vertical rows of uniform, 

 imperforate, plain primary tubercles resembling those of the am- 

 bulacra, diminishing in size and number away from the ambitus ; 

 miliaries and secondary tubercles scattered actinally, arranged 

 around tlie primaries dorsally. 



Peristome circular, with, small branchial incisions ; buccal mem- 

 brane with, plates in continuation wdtb tlie ambulacra, carrying 

 pedicellarise and tentacles ; the rest bare. 



Perignatbic girdle witb low ridges and well-developed pro- 

 cesses. 



Spines moderate, tapering, cylindrical, stout, sharp, longest 

 dorsally. 



Becent. Pacific Ocean, Society Islands, Zanzibar, Natal. 



Grenus Pseudoboletia, Troschel, 1869, Verhandl. d. Naturliist. 



Ver. preuss. Bheinl. u. Westfalens, ser 3, vol. vi. p. 96, pi. 26. 



A. Agassiz, 1873, Bevision, p. 454. J. Bell, 1881, Broc. Zool. 



Soc. p. 433. Be Loriol, 1883, BcJi. de Vile Maurice, p. 28. 



Test moderate and large, circular in tumid ambital outline, 



mucb broader than high, subcorneal, depressed dorsally, and flat 



actinally. Coronal plates numerous, low and broad. 



Apical system small, with the basal plates unequal in size, 

 madreporite in the largest ; two postero-lateral radial plates 



