THE 
VOYAGE OF H.M.S. CHALLENGEE. 
ZOOLOGY. 
REPORT on the Tetractinellida collected by H.M.S. Challenger during the 
Tears 1873-76. By W. J. Sollas, M.A,, D.Sc. Cambridge, LL.D. 
• yV/ 
Dublin, Professor of Geology and Mine-talogy in the University of 
Dublin; late Fellow of St. John’s College, Cambridge. 
PREFACE. 
The TetractineUid Sponges brought home by the Challenger Expedition were sent to me 
for description by Mr. John Murray on the 15th of July 1882. Numerous unforeseen 
interruptions, one of the chief being a removal from Bristol to Dublin, will account for 
the delay which has occurred in the completion of the Report. 
It was not to be expected that a complete separation of the TetractineUid from the 
Monaxonid sponges should be accomplished at one operation, and I have continued to 
receive from time to time additional specimens from my colleagues, Messrs. Ridley and 
Dendy, the last reaching me so late as the close of last year (1886). In this connection 
the uncertainty attaching to the systematic position of the Tethyidse has proved a source 
of great perplexity, and the specimens of this group have changed hands more than once. 
Messrs. Ridley and Dendy could find no place for them among the Monaxonida, and I 
was unwilling at first to disturb the symmetry of the Tetractinellida by including in it 
sponges which do not possess TetractineUid spicules ; when, however, this appeared to be 
inevitable in the case of Placospongia, a genus which is united to the Geodiidse by the 
presence of sterrasters, but which is certainly without any TetractineUid spicules, this 
objection could not be pressed, and I undertook to describe the Tethyidse under the 
impression that they bore much the same relation to the Stellettidse that Placospongia 
(ZOOL. CHALL. EXP. — PAKT LXIII. — 1888.) Rl’l’ « 
