400 ECHINAXIA AND RHABDOSIGMA, 



plate, proxinially contracted into a short and stout stalk, and 

 subdivided marginally into a series of short digitiform, or mammi- 

 form lobes, and provided also with (a few) additional similar 

 lobes arising ndventitiously from its sides. Probably the habit 

 of the species is often simply flabellate, or, more precisely, digito- 

 tiabellate; but in the present instance the lamina is vertically 

 folded, and partially concrescent with itself along one edge, so 

 that its shape in horizontal cross-section is roughly that of the 

 figure 6. In consequence of this, and of the laterally-arising 

 lobes, the essentially lamellar form of the sponge is considerably 

 obscured (Plate xxi., fig.2). The specimen, which is imperfectly 

 preserved in alcohol, measures 70mm. in height, 65mm. in width» 

 and about 40mm. in total thickness; the thickness of the lamina 

 (as also the diameter of the lobes) varies from 10 to 15mm.; and 

 the length of the longest lobe is 25 mm. On the summit of each 

 lobe are from two to seven small, circular oscula, from 1 to 

 (rarely) 2 mm. in diameter, arranged usually in one or two 

 straight rows; and traversing the lobe longitudinally throughout 

 its entire length are a corresponding number of main excurrent 

 canals. On some of the lobes there is observable, radiating 

 towards the oscula, a series of faintly marked grooves or shallow 

 fissures; but these are probably only accidentally-caused cracks. 

 Owing to its abrasion, the dermal membrane is almost entirely 

 wanting; but from traces of it remaining here and there on the 

 less exposed portions of the surface, it would appear to have 

 formed, when intact, a very thin and closely adherent layer, non- 

 separable from the underlying tissues, and finely granular on the 

 surface. Subdermal spaces are indiscernible. Where the dermal 

 membrane is wanting, the surface presents a somewhat velvety 

 aspect, -due to the numerous slightly projecting points of the 

 terminal spicules of the main skeletal libres,— and is dotted (at 

 distances apart of about 1 mm.) with small pinhole-like "pores;" 

 these latter are, of course, not the dermal pores (as the original 

 de.scription would suggest), but the (subdermally situated) 

 orifices of the main incurrent canals. The consistency of the 

 sponge is firm and tough, compressible and resilient; the texture, 

 dense. The colour in alcohol is light brown. 



