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



4. Spongaster pentacyclus, n. sp. 



Arms at equal distances, forming a rectangular, regular cross, of the same size and form as the 

 circular central disk, so that the dark interior part of the shell is composed of five equal circular 

 disks, situated in a quincuncial manner. Tlie clearer complete patagium, enveloping the whole cross 

 perfectly, forms a regular square with rounded edges. 



Binunsions. — Radius of the arms 0-2 ; diameter of each of the five circular disks 0-01 ; length 

 of the square side 0"35. 



Habitat. — West Indies, Cuba, surface (Thomson). 



Subgenus 2. Spongastromma, Haeckel. 



Definition. — Cross formed b)^ the four arms bilateral or u-regular, with the arras 

 at different distances. 



5. Spongaster orthogonus, Haeckel. 



Spongocyclia orthogona, Haeckel, 1862, Monogr. d. Eadiol., p. 471, Taf. xxviii. fig. 3. 

 Spongodisctis orthogonus, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. BerUn, 

 p. 844. 



Arms at different distances, forming a bilateral cross, grouped in two opposite pairs of equal size 

 and similar form. Arms club-shaped, about as long as the diameter of the central circidar disk, 

 enveloped perfectly by the complete patagium, which forms a regidar rectangle, the longer side of 

 which is one and a half times as long as the shorter side. (The arms in my figure are not distinctly 

 enough marked.) 



Dimensions. — Rathus of the arms 0'08, breadth 0"02 ; length of the larger side of the rectangle 

 015, of the smaller 01. 



Habitat. — Mediterranean (Messina), surface. 



6. Spongaster scyllaeus, Haeckel. 



Spongoq/dia sajUaea, Haeckel, 1862, Monogr. d. Radiol., p. 471, Taf. x.xviii. fig. 4. 

 Spongodiscus sayllaeus, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 

 p. 844. 



Arms at different distances, forming a bilateral cross, grouped in two opposite pairs of different 

 size and form, one pair smaller and less divergent than the other. Arms club-shaped, little longer 

 than the radius of the central • circular disk, enveloped perfectly by the complete patagium, which 

 forms a trapezium ; the convergent longer sides of the latter are one and a half times as long as 

 the larger, and twice as long as the smaller parallel side. (The ai-ms are in my figure, loc. cit., 

 not distinctly enough marked.) 



Dimensions. — Radius of the arms 0-12 to 0'14, breadth 0'02 ; length of both convergent sides 

 0'24, of the larger parallel side 0'18, of the smaller 0'12. 



Habitat. — Pacific, central area. Station 272, surface ; Mediterranean (Messina). 



