﻿SPOJSIGES.-HALLMANN. 2IQ 



Introductory Remarks. — I have already pointed ouf (p. 179) 

 that the two sponges (not three as Whitelegge supposed) 

 described by Lendenfeld under the name of Thalassodendron 

 Yuhcns and distinguished as \-arieties dura and lamella respec- 

 tively, belong to different species, and that in their original 

 descriptions the two were confused. This I have been enabled 

 to establish owing to the fortunate circumstance that the 

 actual specimen figured by Lendenfeld under the latter name is 

 still in existence. This specimen, strangely enough, is labelled, 

 in Dr. Lendenfeld's handwriting, '"Thalassodendron riibens, 

 var. dura;" and thus it appears certain that the name dura 

 was purely a manuscript one used in connection with the latter 

 variety, and that its application to the former, for which it is 

 extremel}- inappropriate, was due to inadvertence. Luckily, 

 however, there are nomenclatural reasons why this name 

 should be rejected. 



Description. — The sponge is profusely ramose and attains to 

 a considerable size. Its chief external characteristics lie in the 

 mode of branching and in the occurrence at irregular intervals 

 over its surface of stellate groove-groups ("asterisks"). 



The branches, which in their internodal portions are — 

 roughly speaking — cylindrical (6 to 12 mm. in diameter) or 

 only slightly compressed, become at intervals much broadened, 

 forming nodes of more or less triangular shape. The forma- 

 tion of such a node is almost invariably followed by a division 

 of the branch into a number (two to five or more) of secondary 

 branches. The secondary branches arise from the distal side 

 of the nodal region either on the same level or consecutively in 

 close succession ; the mode of branching might in either case 

 — though less correctly so in the latter — be described as poly- 

 tomous. The resultants of any one polytomy, but usually not 

 of successive polytomies, lie in the same plane. Owing to the 

 rapid multiplication of branches in this way, the transverse 

 dimensions of the sponge increase rapidly upwards. The 

 branches are usually crooked, and this, in conjunction with 

 their frequent anastomoses tends to bring about the formation 

 of a tangled and reticulate mass in which the mode of branch- 

 ing may become more or less obscured. The "asterisks" 

 — groups of radiately-disposed, shallow, sharply-incised fur- 

 rows — occur chiefly on the more compressed parts of the 

 branches; as a rule their centre-points lie on or near the 

 margins of the branches. Quite commonly the central region 

 of the area occupied by such a group is raised up into a con 

 spicuous conical process, to the apex of which the grooves 

 ascend. The number of furrows which arrive at the centre of 

 an asterisk varies from about six to ten ; each of these main 

 furrows usuallv results from the confluence of a number of 



