78 SILICEOUS SPONGES. 



Kalpinella rugosa, Hinde, n. sp. (Plate XIX. fig. 2.) 



Sponge massive, expanded cup- or vase-shaped, with corrugated and folded walls 

 in the upper portion of the cup, the under surface either smooth or with nodose 

 outgrowths. Only the upper portion of the simple cylindrical stem preserved. The 

 walls vary from 17 to 23 mm. in thickness. A fairly large specimen is 230 mm. 

 wide at the summit of the cup, and 110 mm. in height. 



The canal and spicular structures resemble those of the last species, from which this 

 is mainly distinguished by its thicker and folded walls and its larger dimensions. 



Distribution. Upper Green Sand: Warminster, Burbage, Wiltshire. 



Genus THAMNOSPONGIA, Hinde, n. g. 



Sponges growing in the form of simple upright branching stems, or forming bush- 

 like masses. The branches cylindrical or rarely compressed. 



With the exception of one species, in which canals do not appear to be present, 

 these sponges are traversed longitudinally by one or more canals. 



The interior skeleton forms a close mesh, composed of very minute spicules with 

 short stumpy arras. The arms are covered with relatively large prominent tubercles, 

 in such a manner that they appear in some instances to be made up of closely set 

 tubercles or rings. These spicules appear to be connected together either by the 

 interlocking of the tubercles of adjoining spicules or by the adpression of the 

 extremities of the spicular arms, but they do not form distinct nodes at their points 

 of junction with each other. 



I propose this genus for a group of sponges which closely resemble, as regards 

 their form and mode of growth, some species of Poltjjerea and Astrocladia, but 

 present a very different form of mesh-spicule. In both these last-named genera the 

 spicules of the mesh have smooth arms and form prominent junction-nodes; but in 

 the present genus the spicules are tuberculated throughout, and the nodes are incon- 

 spicuous. The characters of the dermal layer also vary from those of Astrocladia, 

 in which no regular trifid spicules are present, whilst these form well-recognized 

 features in the dermal layer of this genus. The character of the interior spicules, 

 and their mode of union with each other, exhibit some similarity to the spicular 

 structure in Plinthosella ; but the mesh is much closer and the spicules are far smaller 

 than in any sponge of that genus, whilst the form of the spicules of the dermal 

 layers is altogether distinct. 



The examples of this genus appear to be abundant in the Upper Chalk, and they 

 usually occur in the interior of flints, frequently loose, so that when the flint is 

 broken the sponge may be extracted. As a rule, the interior skeletal structure is 

 destroyed, but the dermal layer is partially preserved, and the spicules in it can be 

 determined. I refer, provisionally, to this genus also a specimen from the Grey 



