KALPINELLA. 77 



The mesh-structure of the interior is relatively close, composed of small four- 

 rayed spicules with short, robust, smooth arms, and branching tuberculated extre- 

 mities. No dermal layer has been preserved. 



I place in this genus a group of sponges which in form closely resemble some 

 species of Che7iendo])ora, and can only be distinguished therefrom by an examination 

 of the spicular structure, which is distinctly Tetracladine. The absence of the 

 dermal layer prevents a comparison with the recent genus Discodermia ; there is 

 hardly a doubt that the fossil forms were originally furnished with a surface-layer ; 

 and should future discovery show that its spicular structure resembles that of Disco- 

 dermia, the present genus will have to be relinquished, as the interior spicular 

 structure is very similar to that of the recent genus. 



With one doubtful exception from the Grey Chalk, all the sponges of this genus 

 come from the Upper Green Sand, and, in common with most of the examples from 

 the same beds, retain the spicular mesh of the interior in good preservation, but the 

 minute structure of the exterior surface is obliterated. 



Kalpinella PATERiEFOKMis, Hinde, n. sp. (Plate XVIII. fig. 4, and 

 Plate XIX. figs. 1, 1 «, 1 h.) 

 1831. PoJypothecia e/rpansa?, Benettj Cat. Org. Rem. Wilts, t. 6. f. 2. 



Sponges cup-shaped, in some cases shallow and expanded, in others moderately 

 deep. The stem is either short and compressed or elongated and cylindrical. The 

 margins of the cup are rounded, and sometimes exhibit open canals. The wall 

 varies between 12 and 18 mm. in thickness in different specimens. A small example 

 is 70 mm. in width across the cup, and a large specimen 110 mm. The longest stem 

 preserved measures 93 mm. 



The canal-apertures are from 1 to 1-5 mm. in width ; they are nearly equal in 

 size, so far as can be ascertained, on both the upper and under surfaces of the cup- 

 wall; in some specimens the canals of the under surface open very obliquely 

 downwards. 



The spicular rays of the interior are very irregular in length, and from '02 to 

 •04 mm. in thickness. The extremity of the rays is developed into a bunch of 

 tubercles, and by the interlocking of the tubercles of adjoining rays the mesh is 

 built up. In some of the spicules the canals of the interior are still preserved ; they 

 extend from the centre of the spicule to about half or two thirds the length of the 

 arms, and appear as very minute cylindrical tubes. 



In external form some of the specimens resemble the Polypothecia expansa, Benett ; 

 but in the absence of all description of the internal structure of this species, I have 

 deemed it best to place these forms under a fresh designation. 



Distribution. Upper Green Sand : Warminster. Doubtfully from the Grey Chalk 

 near Folkestone. 



