216 PANAMIC DEEP SEA ECHINI. 



As there are no detailed figures of Moira, I have given the principal 

 features of Moira clotho, the Pacific representative of the genus. This species 

 is very regularly oval when seen from ahove (PI. 109, fig. #). The odd 

 anterior ambulacrum is bare, covered with minute miliaries, slightly sunken 

 at the ambitus; it is somewhat dumb-bell shaped, deeply sunken towards 

 the abactinal pole. The abactinal plates are narrow and increase rapidly in 

 size toward the ambitus, where it is crossed by the peripetalous fasciole. 



The ambulacral plates of the sunken petals are quite uniform in size ; at 

 the extremity of the petals they pass suddenly into horizontally elongate 

 plates, which in their turn pass on the actinal side into bare, longitudinally 

 elongated plates. 



The coronal plates are covered with rather small tubercles very uniform 

 in size, arranged in diagonal rows across the plates. In the larger interam- 

 bulacral and ambulacral plates of the sides of the test the lines of tubercles 

 are interrupted by bare spaces (PI. 109, figs. 2, .,'). 



On the actinal side (PI. 109, fig. 1) the tubercles are much larger, espe- 

 cially on the plastron towards the actinostome and on the interambulacral 

 areas along the bare ambulacral areas. The left plate of the sternum is 

 larger than the right (PI. 109, tig, /), the labium is very prominent (PI. 109, 

 fig. .*'), with the actinal sternum forming a very marked keel ; the primor- 

 dial plates of the posterior interambulacra are irregularly triangular and in 

 contact with the actinostome by a mere point. Those of the anterior 

 interambulacra are L-shaped and arc in contact with the actinostome by a 

 broader face (PI. 109, fig. /). 



The actinostome is transverse with a convex labium (PI. 109, fig. 7); 

 the anterior edge is bordered by eight large irregularly rectangular plates 

 with an inner row of smaller plates and a third still smaller row adjoining 

 the labium. 



The anal S3'stem is longitudinally elliptical (PI. 109, fig. 8), flanked by 

 an outer row of eight large polygonal plates and two irregular rows of 

 smaller plates radiating from the anal opening. 



We may note that M. de Meijere ' mentions a species of Moira from the 

 East Indian Archipelago. The profile and abactinal views given by him 2 

 are said to be from the same specimen ; they are drawn on a different scale. 

 This may be a young specimen of the species of Moira (M. stygia) said to 

 inhabit the Red Sea and to be found on the east coast of Africa (Zanzibar). 



1 " Siboga" Eehinoidea, p. 183. 2 Id. PI XXII, figs. 450, 460. 



