658 R. KIRKPATIUCK. 



section showed a series of vertical tubes divided up by 

 horizontal partitions or tabulae. The vertical walls were 

 imperforate, but marked with longitudinal vertical sutures ex- 

 tending from the upper surface to the base, one suture being 

 between any two tubercles. The horizontal tabulae usually 

 had a central hole or slit, but were sometimes imperforate. In 

 the uppermost spaces of this honeycomb-like framework were 

 bundles of slender pin-shaped spicules. In the small frag- 

 ment that could be spared for the making of preparations I 

 found a "tuning-fork" spicule, seemingly imbedded in one 

 of the tabular (PI. 38, fig. 6). 



Apparently the pin-shaped spicules were not present in the 

 particle of Merlia used for decalcification, and I wrongly 

 concluded that these spicules were calcareous and that they 

 had been dissolved in the acid. 



I named the incrusting organism Merlia normani, and 

 regarded it as a Phareti'onid sponge.^ (1) Even if I 



^ If it bad been lawful to base any opinion at all on the investigation 

 of such scanty material, then the conclusion arrived at was, I think, a 

 legitimate one. " Tuning-fork " spicules with thick, parallel, wide-apart 

 prongs have been found only in Pharetronid sponges. Finding this 

 rare and pecviliar form of spicule seemingly imbedded in one of the 

 tabula of a mysterious calcareous skeleton unlike that of any known 

 recent organism, it seemed justifiable to conclude that the spicule 

 belonged to the framework, and that therefore the latter had been 

 made by a calcareous sponge. The upper surface of tlie skeleton of 

 Merlia shows, too, certain resemblances to that of the Pharetronid 

 sponges, Porosphsera and Plectroninia. Further, a Pharetronid 

 — Murrayona phanolepis, Kirkp. (' Proc. Roy. Soc.,' 1910) — has 

 now been found, in which solid skeleton fibres are devoid of an axial 

 core of spicules, and it was on these characters that I founded the sub- 

 family Merlinaj. The spicule, which sent me on the wrong track, was 

 a genuine " tuning-fork " and not a simulacrum made by some boring 

 fungus or Alga, for when I crushed under the cover-slip the fragment 

 of sponge containing the spicule, the latter floated out solid and free 

 into the balsam. At present only three Pharetronid Lithonine sponges 

 are known with a similar kind of tuning-fork, and these have been 

 recorded from the Indian Ocean and Pacific. Off Porto Santo Island, 

 in submarine holes or caves, possibly almost inaccessible to dredges, 

 there miist be a Pharetronid sponge. Unfortunately I failed to secure 

 examples, in spite of twelve days' dredging. 



