Prof. W. Thomson on the Deep-sea Dredging-expeditions. 305 



Ananchytid^e. 



Pourtalesia, A. Agassiz. 



According to the c]assi6cation of Desor, which makes the "dis- 

 junct " arrangement of the ambulacra at the apex the test character 

 of the Dysasteridse, this genus should be referred to that group ; for 

 the apical disk is truly decomposed as in Dysaster and Collyi-ites, 

 and not merely drawn out as in Ananchytes. From the arrangement 

 and form of the pore-plates, however, and from the general appear- 

 ance and habit of the animal, I am inclined to think with A. Agassiz 

 that its affinities are more with such forms as Infnlaster. Pourta- 

 lesia must be an aberrant form, in whatever group it may be placed. 

 The mouth is at the bottom of a deep anterior groove, occupying the 

 anterior ambulacral area. The arrangement of the trivium is nearly 

 normal ; but the bivial region is enormously prolonged backward 

 into a long rostrum, on the upper surface of which, near its pos- 

 terior extremity, the anus is situated in a pit partially covered by a 

 projecting boss. The ambulacral pores are simple, one pore on each 

 plate. 



1. P. Jeffrey si, n. sp. 



A single specimen of this very remarkable form was dredged in 

 G-JO fathoms to the north of the Sbetlands. It is nearly allied to 

 P. miranda, Pourtales, from the Strait of Florida, but differs in several 

 details. 



2. P. phyale, n. sp. 



Two or three small specimens were dredged by Mr. Gwyn Jeffreys 

 in the Rockall Channel. All the specimens are immature; but from 

 the marked difference in form, and from some other characters, I 

 believe them to be the young of a second species. 



Spatangid^. 



Brissopsis, Agassiz. 

 1. B. lyrifera, Forbes, sp. 



Large specimens of this species are abundant at from 50 to 250 

 fathoms. Beyond the latter depth the specimens decrease in size, 

 and at extreme depths only examples which have all the appearance 

 of being very young are met with. These small delicate specimens 

 were found at all depths, even down to 2090 fathoms. 



Tripylus, Philippi. 

 1. T.fragilis, D. & K. 



At from 400 to 500 fathoms between Scotland and Fsercie. Hitherto 

 known as Scandinavian. 



Schizaster, Agassiz. 

 1. S. canaliferus, Val. 



A single small specimen from the coast of Spain. 

 Amphidetus, Agassiz. 

 1. A. nvatus, Leske, sp. 



Abundant at moderate depths. 



Spatangus. 

 1. S. purpureus, O. F. Miiller. 



