272 PEOr. p. M. DUJfCAN's KEVISION OF THE 



lateral basal plates, but not uniting centrally in consequence 

 of the madreporite. 



Anterior ambulacrum in the front part of tbe depression, larger 

 than the others ; its rows of pairs of pores far apart and the pores 

 larger than those of the other ambulacra. The antero-lateral di- 

 vergent, and the postero-lateral passing back at a small angle 

 and very long ; both narrow, flush, apetalous, witli small plates, 

 each with a pair of pores above tlie ambitus, and with large 

 pores in peripodia around the peristome ; the plates of the 

 posterior pair very long actinally on either side of the sternum ; 

 pairs of pores very few in number. 



Interradia with very mucli larger plates than the ambulacra, 

 the postero-lateral very broad, a long narrow peristomial plate in 

 front of a true and more or less keeled amphisternum ; other 

 peristomial plates narrow. 



Peristome excentric in front, circular, with the labrum 

 projecting on a lower level than the opening. Periproct dorsal, 

 flush, and elliptical, pointed forwards, somewhat remote from the 

 posterior end of the test ; membrane with concentric plates. 



Tubercles small, somewhat numerous on the abactinal inter- 

 radial plates, one on each ambulacral plate dorsally, largest on 

 the sternum. 



A broad fasciole extending obliquely from close behind tlie 

 vertex, which is subcentral, around the edges of the anterior 

 depression and curving actinally close to the anterior margin, 

 crossing the ambulacra and including a broadly elliptical space ; 

 apparently the pores of the paired ambulacra are uniporous below 

 the fasciole. 



A few very large disciferous tentacles in two rows in the 

 anterior ambulacrum ; and some large penicillate tentacles 

 around the peristome. Spines, some club-shaped, the others 

 acuminate cylindrical ; the first kind commonest actinally and 

 behind the fasciole, spathiform and large upon the sternum, 

 hollow, longitudinally ridged. 



Becent. Davis Straits, Bay of Biscay, coast of Portugal, 

 E. coast of U. States, 130 miles from Sandy Hook, Arafura Sea. 

 800 to 1750 fathoms. 



In the beautiful drawing given in the ' Challenger ' Eeport, 

 pi. xxxiii a. fig. 10, there is a possibility of the existence of a 

 fifthi imperforate basal plate. It is very important that separate 

 descriptions of the specimens from Davis Straits and the 

 remote Arafura Sea should be presented to science. 



