OP ARTS AND SCIENCES. 201 



rathei irregularly placed. On the actinal membrane the tubercles of 

 both areas are identical in size, forming regular concentric rings 

 broken by the bare spaces in the median areas round the actinostome. 

 The spines of the actinal surface are more or less trumpet-shaped at 

 the "extremity, with well-worn tips ; those of the abactinal region are 

 pointed and generally covered by a loose muscular sheath extending 

 beyond the end of the spine, forming a series of swellings, from four 

 to six, around the sharp cylindrical spine which it encloses. — Zam- 

 boanga, 10 fathoms. 



Asthenosoma coriacea, A. Ag., nov. sp. 



Distinguished from the preceding by its broader primary plates and 

 by having similar spines on both the actinal and abactinal surfaces. 

 The primary tubercles are few in number, limited mainly to the prox- 

 imity of the edge of the test, both on the actinal and abactinal sides. 

 One principal row extends to the abactinal area on the edge of the 

 interambulacral plates of the abactinal side, and one on the actinal side. 

 The remainder of the interambulacral plates are closely covered by 

 small secondary tubercles or miliaries. In the ambulacral area the 

 large primary tubercles extend only over a few plates on each side of 

 the middle of the test. — Station 204, 100 fathoms ; Station 173, 310 

 fathoms ; Tongatabu ; Station 299, 2,160 fathoms. 



Asthenosoma tessellata, A. Ag., nov. sp. 



The specimen on which this species is established may prove to be 

 only a younger stage of the preceding. It presents, however, such 

 ^striking features in the extremely regular arrangement of its plates, 

 both on the actinal and abactinal sides, and their uniform size both in 

 the ambulacral and interambulacral areas, that for the present it may 

 be convenient to distinguish this species from A. coriacea until we 

 know something more of the changes this group of Echini undergo 

 during growth. 



The same remarks apply to a number of small Asthenosoma? 

 and Phorrnosomae which, unfortunately, coming from many different 

 localities, I am unable, on account of the great differences they show 

 from the fully-grown forms, to associate them at present with any of 

 the species here described. — Station 200, 250 fathoms. 



Phormosoma luculenta, A. Ag., nov. sp. 



This species is readily distinguished from the others of the genus 

 by the greater solidity of the test, its pinkish or violet color seen 



