CLARK: AUSTRALIAN AND INDO-PACIFIC ECHINODERMS. 135 



trideutate aud triphyllous are abundant. Color of test deep brown in alcoholic 

 specimens, becoming bright brown when dry ; spines, green abactinally, but 

 greenish-brown on the actiual surface ; hoofs of the primaries, white. 



Off Botany Bay, New South Wales, 80 fins. 



An excellent series of ten specimens of this interesting echinothurid are in the 

 M. C. Z. collection. They were received in exchange from the Australian 

 Museum, and are labelled "Phormosoma hoplacantha." This is undoubtedly the 

 species to which Mr. Waite refers in his introduction to the reports on the collec- 

 tions of the " Thetis," when he says that " in eighty fathoms off Botany Bay, 

 between two and three hundred examples of the rare echinoderm Phormosoma 

 hoplacantha Wy. Thompson, were hauled on board. This find was specially 

 interesting as the animal had previously been taken only by the ' Challenger ' at 

 the minimum depth of 410 fathoms." 



The relationship of A. thetidis, however, is not with the deep-water species like 

 A. hoplacantha, but with the shallow-water forms like Asthenosoma owstoni (Mor- 

 tens.), to which it seems to be nearly allied. It may be distinguished from that 

 Japanese species, however, by the larger and less numerous primary tubercles, the 

 much higher actinal coronal plates, the more regular arrangement of the actinal 

 interambulacral tubercles, the much wider ambulacra, and the very different 

 color. I take pleasure in associating with this interesting species the name of 

 the vessel to which we owe its discovery. 



