— /i65 — 



diameler. A sLyle as in other species. Dactyiopores protected on Ihe ter- 

 minal branches by very shallow grooved ridges representing tlie grooved 

 spines of other species. On the larger bronches thèse grooved ridges are 

 absent. Bolh gasteropores and dactylopores very scarce and principally 

 found on the sides of the branches as in Distichopora. 



Colour : pure white. 



Localities : 998-900 m. Azores, 358 m. S. du Fayal. 



Genus Plîobothrus Pourtalès. 



ïhis genus vi^as originally described by Pourtalès [Bull. Mus. Comp. 

 ZooL , 7 ) but more fuliy investigated and described by Moseley ( Challenger 

 Reports, 2). It is not necessary to add anything to the excellent diagnosis 

 given by the latter. 



The genus eau be readily distinguished from other Stylasterina by the 

 foUowiug three characters : 1° the absence of styles in both gasteropores 

 and dactylopores; 9° the tubular opening of the dactylopores; 3° the large 

 chambers at the base of the gasteropores. 



At first sight, spécimens of PKobothnis might be mistaken for a species 

 oîErrina, but the absence of a slit on one side of the tubular projections 

 that protect the openings of the dactylopores forms a distinction that can 

 be readily seen witli a magnifying glass, and the generic distinction can 

 be confirmed by an examination of a section of the branch which is solid 

 in Errina, but marked by large honeycomb spaces in PKobothms. 



Only two species hâve been described , PUobothrus sijmmetricus and P. tu- 

 hulaiiis. They were bolh found on the western slopes of the Atlantic Océan 

 in depths of 98-970 fathoms and according to Duncan P. symmetrîcus was 

 also found in 5oo-6oo fathoms north of the British Islands [Trans. Zool. 

 Soc, VIII, 1874, p. 336). The principal différences between the two 

 species appear to be that P. symmetrîcus is more robust in growth and the 

 terminal ends of the branches are thick and rounded at the extremity in 

 contrast to the délicate finely pointed branches of P. tubulatus. The tubu- 

 lated dactylopores are more projecting in P. tubulatus than in P. symme- 

 trîcus. 



It is possible that future investigations will prove that the two species 

 cannot be separated , but I am inclined for the présent to place oue of the 

 spécimens coUected by the Talisman in the species P. symmetrîcus and the 

 others in the species P. tubulatus notwithstanding the fact that the latter 

 are not so hirsute as the type spécimen is , judging from the figure of it 

 that is given by Pourtalès. 



AU the spécimens coUected by the Talisman were obtained in the same 

 dredging ofFthe Azores in 56 mètres. 



Manchester, Aug. 10-1912. 



