60 THE VOYAGE OF H.M.S. CHALLENGER. 



presence of " anchorate " microsclera (chelse)/ while Schmidt's typical species of the genus, 

 Vomerula tencla,^ does not possess these; on the other hand, the genns differs from 

 Hamacantha, Gray, in a point unnoticed by Vosmaer, viz., the possession of well- 

 marked stylote megasclera, and on this account the two genera Hamacantha and 

 Vomerula may at present remain separate. This difference is, however, perhaps not so 

 important as would at first sight appear, as the so-called oxeote of Hamacantha johnsoni 

 is frequently slightly blunted at one (or both) ends, and therefore seems to be possibly 

 derived from a stylote spicule or to have given rise to that of Vomerula ; (this tendency 

 to bluntness is indicated, but perhaps too strongly, in Bowerbank's original figure).^ On 

 the other hand, there is one preparation in the Bowerbank collection, from a species 

 identified by him with Hamacantha johnsoni, in which the oxeote spicules are well 

 pointed at both ends, with no noticeable tendency to blunting. This greatly supports 

 us in distinguishing two genera of the subfamily. 



Vomerula esperioides, Eidley and Dendy (PL XII. fig. 1; PI. XVII. figs. 2, 4, 12). 



1886. Vomerula esperioules, Eidley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol xviii. 



p. 337. 



Sponge (PL XII. fig. 1) large, erect, forming tall, thick, leaf-like expansions, attached 

 by the base, reaching about 250 mm. in height by about 50 mm. or more in 

 breadth and 25 mm. in thickness. Colour in spirit pale yellow. Texture tough and 

 strono-, owino- to the very coarse fibres of the skeleton ; but the interior is cavernous. 

 Surface uneven, with numerous small prominences (conuli) caused l»y the projecting 

 ends of the underlying fibres of the skeleton. Supported upon, and stretched tightly 

 between these prominences is a thin transparent dermal membrane, covering over the 

 large, irregular, subdermal cavities. The dermal membrane (PL XVII. fig. 12) contains 

 very numerous round pores, 0"07 mm. in diameter, which lead from the exterior into 

 the subdermal cavities ; the boundaries of these pores are supported by numerous small 

 sio-mata arranged around them. The dermal membrane is further supported by a 

 reticulation of fine fibres, yet easily visible to the naked eye, which gives a highly 

 characteristic appearance to the surface. The oscida are placed on the summits of 

 small, conical, bladder-like papiUae (PL XII. fig. 1), bounded only by the dermal mem- 

 brane, in which there are here no pores. Over these papillae the dermal reticulation 

 of fine fibres is absent and its place is taken by a single layer of closely placed 

 spicules, in which the styli are mostly arranged longitudinally and more or less parallel 

 v/ith one another. 



1 Bronn's Klass u. Ordn. A. Thierreichs, Porifera, p. 352. ' Spong. Meerb. von Max., 1880, p. 82. 



3 Mon. Brit. Spong., vol. i. pi. xviii. fig. 293. 



