930 THE VOYAGE OF H.M.S. CHALLENGER. 



3. Polyplecta decacantha, n. sp. 



/ 



Pentaplegma decacantha, Haeckel, Prodromus, p. 425. 



Ten radial spines, curved, cylindrical, irregularly branched, diverge in different directions 

 and seem to arise in pairs from an irregular central framework, in the centre of which five 

 primary spines are united ; the latter correspond probably to the five spines of Pentaspyris, &c. 

 The density of the spongy central framework did not allow of an accurate investigation, and makes 

 it doubtful whether this species is not a Spongiomma. 



Dimensions. Length of the spines 0'3 to 0'4, diameter of the framework 0'18. 



Habitat. Tropical Atlantic, Station 338, depth 1990 fathoms. 



4. Polyplecta polybrocha, Haeekel. 



1 Acanthodesmia polybrocJia, Haeckel, 1865, Zeitschr. f. wiss. Zool., Bd. xv. p. 368, Taf. xxvi. 



fig. 3. 

 Plegmosphcera polybrocha, Haeckel, 1881, Prodromus, p. 455. 



Numerous (twenty to thirty or more) radial spines, thin, cylindrical, curved and irregularly 

 branched, arising from an irregular central spongy framework, are connected by numerous slender 

 arches. The specimen observed by me in 1880 in Portofino was a true Polyplecta, with three 

 primary spines centrally united, between which numerous other spines were intercalated. The 

 similar specimen, however, observed in 1864 in Villafranca, and figured, loc. cit., was perhaps a 

 Plegmosphcera. 



Dimensions. Length of the radial spines 0'05 to O'l, diameter of the framework 016. 



Habitat. Mediterranean (Villafranca, Portofino), surface. 



5. Polyplecta dumetum, Haeckel. 



Acanthodesmia dumetum, J. Miiller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 30, Taf. i. 

 fig. 3. 



Numerous (ten to twelve or more) radial spines, thin and straight, with a few straight lateral 

 branches, diverge in different directions and are connected by a few slender curved arches. Some 

 similar forms, but more developed, with numerous branches and curved rods, are found in the 

 Pacific Eadiolarian ooze, and represent probably different species. 



Dimensions. Length of the radial spines 0'05 to 0'08, of the branches 0'02 to 0'03. 



Habitat. Mediterranean, French shore (Cette and Saint Tropez), Johannes Miiller, surface 



