98 SILICEOUS SPONGES. 



small, upward projecting, cylindrical or compressed tubes, which are open above. 

 Neither the summit nor basal portion is preserved in the specimens. The example 

 figured by Smith is 61 mm. in height and 30 mm. in width. Another imperfect 

 specimen in the Museum is 86 mm. in height and 61 mm. in width. The projecting 

 tubes are from 3 mm. to 7'6 mm. in diameter, and in length from mere projecting 

 cups to tubes 176 mm. in length. The thickness of the spicular wall is about 

 1"2 mm. The outer surface of the wall has a delicate lace-like dermal layer com- 

 posed of somewhat thickened spicular arms and nodes. There are minute circular 

 apertures, about "5 mm. in width, in this layer as well as the small interspaces in the 

 mesh itself. The mesh-spicules are small, with solid nodes. I have not been able 

 to determine the characters of the inner surface of the wall. 



From the typical Jurassic forms of VerrucocceUa this species differs in the possession 

 of a modified dermal layer ; but I do not regard this feature as of sufficient importance 

 to place this form in a new genus, but propose to extend Zittel's definition so as to 

 include sponges with a perforate dermal layer. The spicules of the interior mesh of 

 the wall, and the general mode of growth, resemble the typical Jurassic species. 



The specimens are now in the condition of iron peroxide. The figure of this 

 species given by T. Smith represents it in a reverse position. The woodcut (fig. Q) 

 on p. 367, in the 'Annals,' which, according to Smith, represents a transverse section 

 of this species near the top, does not appear to belong to this form at all. 



Distribution. Upper Chalk : South of England. 



Veerucoccelia vectensis, Hincle, n. sp. (Plate XXIV. figs. 3, 3 «, 3 h.) 



Sponge generally conical in form, widest a short distance above the base, and thence 

 tapering to the summit. The only specimen is 152 mm. in height and 100 mm. in 

 greatest width. Numerous cylindrical tubes, from 20 to 35 mm. in length and from 

 11 to 20 mm. in width, spring from the central cavity and project upwai'ds. These 

 tubes are open at the surface ; the margins are rounded. The walls are from 2 to 

 2-6 mm. in thickness, and the interior of the tubes from 5 to 13 mm. in width. The 

 spicular structure of the outer surface-layer is slightly different from that of the 

 interior of the wall in that the arms and nodes of the spicules are somewhat thicker. 

 This reticulate dermal layer is perforated by numerous circular or ovate canal- 

 apertures, about "5 mm. in width. The spicular mesh of the interior of the wall is 

 somewhat irregular, and is composed of robust spicules with compact {i. e. not 

 lantern) nodes. The spicular arms are in places minutely spinous, in other places 

 they appear to be smooth ; they vary from "045 to -067 mm. in thickness, and the 

 distance from one nodal centre to another is about '225 mm. There are also occa- 

 sionally present in the interstices of the mesh very minute delicate hexactinellid 

 spicules, which are only attached by the extremity of a single arm to the mesh 

 itself 



