SPONGIIDA. 463 



forms compose the main bulk of the skeleton. (2) Long smooth 

 acuate, generally slightly curved, tapering gradually to a fine point ; 

 size about !•! by '0127 miUim. : forming part of longitudinal 

 skeleton-lines of surface-tufts. 



Hob. Thursday Island and Prince of Wales Channel, Torres 

 Straits, 4-7 fms. 



Distribution. " African coasts ? " (Lamarclc). 



As pointed out in speaking of the characters of the ends of the 

 branches, this form shows considerable variability : as a rule the 

 specimens are chiefly branched in one plane (fan-like), but in two 

 specimens branches project from both faces, but they then tend to 

 form fan-shaped fronds parallel to the main frond. The largest 

 specimen measures 160 miUim. (6| inches) high by 160 miUam. 

 wide ; the average maximum diameter of the distinct branches 

 (which are cylindrical or somewhat compressed), not that of the 

 broadest but obviously compound branches (which occur commonly), 

 is about 10-12 mUlim. Five specimens occurred. 



91. Acanthella, sp. 



Externally resembling Spongia earduws, Lamarck (Ann. Mus. 

 Hist. Nat. XX. p. 381). When guided by the description alone, 

 I had referred the present specimen to this species with more con- 

 fidence than usual ; but on mounting sections of the probable type 

 specimen at Paris, I saw that it was a difierent species. The 

 points in which the description does not quite suit this form are 

 " pedicule cyUndrace, tres-dur," the stem having apparently been 

 flattish, and, though stiff, not inflexible ; and " couleur d'un blanc 

 grisatre," -whereas this (in spirit) is flesh- colour. The ridges run 

 longitudinally up and down the sponge, and are 1 to 3 miUim. high, 

 and their free edge is beset ■with sharp (in spirit flexible) points at 

 intervals of one or two millimetres. Texture tough and flexible, 

 substance compact, surface between inequalities glabrous. It is a 

 true Acanthella. The spiculation is as follows ; — (1) Smooth acuate, 

 slightly curved, tapering gradually to sharp point, about -4 to "6 

 milHm. by -0095 miUim. (2) Smooth undulating cylindrical with 

 rounded ends, length about "7 miUim., diameter just •0063 miUim. 



The species difiers from the Adriatic forms A. acuta and ohtusa, 

 Schmidt, in the broad explanate^ form and in the smaller size of 

 the spicules, the cylindrical being much shorter and thinner, the 

 acuate much shorter than in those species. The skeleton forms 

 a loose-fibred Aa;inella-]ike network of spicules, imbedded in a 

 dense, transparent, almost colourless mass of caoutchouc-Uke con- 

 sistency, containing nucleoid bodies about "007 to -008 mOlim. in 

 diameter. 



Sab. Prince of Wales Channel, Torres Straits, 7 fms. 



A single specimen in spirit, 35 miUim. (If inch) high by 29 

 millim. across. 



