312 Transactions. — Zoology. 



thickness of 6mm. The surface is compact and minutely 

 granular ; colour varying from light-pink to a yellowish-red. 

 Zooids quite inconspicuous and irregularly arranged. 



The branchial pores are very small and indistinct. In 

 transverse section the branchial siphon has its edge six-lobed, 

 the lobes turning outwards (fig. 4). Inside the branchial 

 aperture is seen closed as in L. niveum by three lobes, much 

 fainter and less granular, hoNvever. The branchial sphincter is 

 well developed in longitudinal sections. 



Common cloacal openings are small and invisible without 

 high magnification (fig. 1, c.c.o.). Cloacal canals are distinct 

 even when the spicules are present (figs. 1 and 2,c.c.). These 

 canals are near the surface, and, as far as present observa- 

 tions extend, never connect with downward passages, lower 

 canals being also absent. 



The spicules (fig. 6) are remarkable, being equal in size to 

 those of L. niveum, but much denser, the rays having their 

 ends in all cases rounded instead of pointed. They are ex- 

 tremely numerous, far more so than in the preceding species, 

 and are most abundant on the upper surface and in a thin 

 layer running parallel to the lower surface at some slight dis- 

 tance above it (fig. 2). Their number is so great that examina- 

 tion is quite impossible except in decalcified specimens, and 

 they give a characteristic brittleness to the corm both in the 

 natural state and in alcohol-hardened specimens. Each spicule 

 is faintly pink in the stained sections — the only case in which 

 colour is present. As only osmic-acid specimens were mounted 

 without previous decalcification, I am inclined to think that 

 the colour of the colony is due to this coloration of the spicu- 

 lar membrane, the colour being in other preparations removed 

 by the alcohol employed. Specimens of L. niveum, also 

 treated with osmic acid, showed no such coloration. No 

 sections in the natural state were available after the discovery 

 was made, otherwise the point might easily be settled. 



The test differs considerably from that of L. niveum in its 

 histological structure. The test-cells are far more numerous 

 and smaller (fig. 3, t.c). They are embedded in a structure- 

 less matrix, which, on careful focussing, reveals numerous 

 clear spaces of polygonal or rounded form, separated from the 

 matrix by a very delicate membrane. This I take to be the 

 spicular membrane (fig. 3, sp.m). The same characters are 

 presented throughout the test, except that these spicular 

 membranes are smaller and more numerous where the spicules 

 are most strongly developed. 



Test-vessels are present (fig. 1, v. op.), in this case uni- 

 formly taking their rise near the termination of the endostyle. 

 A terminal knob is usually present (fig. 7, v.ap.). 



The zooids slightly exceed in length those of L. nivcimi, 



