Sponges from the Atlantic Ocean. 221 



fig. 25) smooth, C-shaped, more or less contort and sigmoid ; 

 average largest size about 21 by 1|— 6000th inch. Equi- 

 anchorate (fig. 24, a, b) consisting of a simple shaft with three 

 linear arms at each end, united to the former respectively by a 

 short falx. Size of entire specimen about ^ inch in dia- 

 meter. Longest tube l-12th inch in diameter and 9-12ths of 

 an inch in length. 



Hah. Deep sea. 



Loc. Atlantic Ocean off the west coast of Ireland. 



Obs. There are specimens of this sponge in two jars, 

 numbered respectively " 2 " and " 24" (i. e. Stations), which 

 would give respectively the depths of 808 and 109 fathoms. 

 In jar No. " 2 " it is in company with Tisiphonia agaricifor- 

 mis, Wy. Thomson, Pachastrella abyssi, Schmidt, Tethya 

 cranium, Hymedesmia Johnsoni, Bk., Halichondria ventila- 

 brum, Geodia, and deciduous fragments of a Corallistes ; while 

 in jar No. " 24 " it is in company only with Hyalonema 

 longissimum, Sars {pp. cit.), and Tisiphonia agariciformis. 



There is a great resemblance in form and structure between 

 this sponge and Melonanchora elliptica, inasmuch as both have 

 the same silvery resilient dermal covering filled internally 

 with soft, pulpy, fibreless parenchyma ; but while in the latter 

 the dermal structure is only extended to the base of the short 

 tubercles with cribriform heads respectively, in the former, or 

 Histoderma, it is extended into the walls of the tubes through- 

 out, terminating abruptly, and followed by the cone of spicules 

 above mentioned, of which unfortunately there is only one 

 example left, the rest of the tubes having been broken off 

 towards their ends. 



With, therefore, no fibrous structure internally, it is evident 

 that the bladder-like dermis is the skeleton or organ of 

 support in these sponges. 



In some specimens the tubes are shorter than in others ; 

 while in others there is nothing but a slight elevation of the 

 surface surrounding a flat or sunken pore-area, but not formed 

 of cribriform sarcode like that of the tubercles in Melon- 

 anchora. 



When dried the specimens present an asbestine appearance 

 from the densely packed spicules of the dermis, which, together 

 with the stiff, horny sarcode that holds them together, forms a 

 textile fabric that retains its form whether wet or dry. 



[To be continued.] 



