50 



The eaiicocoms, which differ from the graphiocoms in several respects, are 

 not numeroDS and rather inegidarly scattered. They sure chiefly met vntk in 

 the snboustral, more rarely io the sobdermal region, and measure about 200 i^ 

 in diameter. Their principal feature are the conic, externally calyx-hke, solid 

 thickenings at the ends of the stout and short main rays and the flower-like 

 verticils of slightly rough branch-rays cnrving gracefully outward which arise 

 from the latter. These are of medium length and uniform thickness through- 

 out; thev arise in BjoIo^u^ nybinvj^ exclusively from the circular margins of the 

 terminal thickening of the maia-rays and accordingly form simple verticils (pL 

 IX, f. 7). In the cahcocoms of other species of Holaseug they arise from the 

 whole of the distal surmce of the terminal thickeniag and accordingly form solid 

 brushes. 



The only specimen of Holoious robmhtg was found in the Bay of Bengal 

 12' 20' X. 85' S E. in a depth of 3300 m. = 18«j3 fths. 



HfAaiseu^ iener F. E. Sch. 



ISBomOmiXMgiemerT. E. Seh. is Abh. Freas. Ai. 1865 pot 7-*. 



The lower part of a tube, 12 mm. wide, with a wall 2 mm. thick, is for a 

 length of 55 mm. sufficiently well preserved to enable one to recognise the 

 principal features of its structure. From the slightly attenuated lower end a 

 basal root-tuft abont 15 Tnm- long and in structure like wickerwork, arises. This 

 tuft probably represents only a small part of the root-tuft of the hving sponge 

 the length of which, in the fresh state, I estimate at 8-10 cm. MacroscopicaUy 

 the sponge does not essentially di^er from S. robmiu^. Also here one sees on 

 the outer surface through the dermal membrane, of which only small parts are 

 intact, the aperture and canals which lead from the subdermal cavities into the 

 interior of the sponge, whilst the inner surfece of the tube- wall shows a quadratic 

 reticulation with meshes containing the openings of the excurrent canals into the 

 central cavitv, arranged in longitudinal and transverse rows. 



The stout principal spicules of the tubular main skeleton are in H.. robustug 

 exclusivelv stauractines (pL IX, f. 8), in H. i^ner nearly always pentactines, four 

 ravs of which are similar to the rays of the stauractines of E. robust us and 

 arranged in the same manner. The fifth ray is vertical to the four others and 

 directed outwards; it attains a length of 360 y- and nearly reaches the outer 

 surface. Onlv very rarely I found, here and there, instead of such a pentactine, 

 a stauractine. Attached to these stout principaha, s imilar ly shaped and ar- 

 ranged, ^onty triactine and diactine comitalia are met with, as in H. rrj/iigfus (pi. 

 IX, f. 9, 10). The macrosclere oxyhexactines, abundant in H. robusius and there 

 f ormino- a layer outside the main tubular reticulation, are absent in H. tener and 

 are here probably functionally replaced by the distal rays of the pentactines in 

 the T^aiTi tubular skeleton-net. 



