18/4.] DR. J. S. BOWERBANK ON THE SPONGIADiE. 303 



into the mineral kingdom, and partly to the mode in which their 

 remains are occasionally preserved." With our present knowledge of 



XcTv the" °f th r Spons v ada3 ' the * reat variet ^ °"Z™ 



accounted 1 ^ ™ y . be naturall y and ™re readUy 



Tower of IZ , RU by ™?? mn S them to have possessed the 



wE »L? °l and dl l atati0n ; and the enveloping flint, 



wh ch affords no indication of the form or structure if the en 

 closed sponge, ,s now known to be attributable to the ventrical? e 

 sponge having, in its living state, been covered by a TaScS 

 body!" SP ° Dge ' the Wh ° le bei " S subse ^ntly fossilized Z ! one 



tte S fvTTp° f Mantell ' S Vent :r lites radiate embedded in flint 

 ;,Z n "^ s uncommon. If one of these exhibiting the natural 

 surface of either the internal or external surface be immersed in a 



uS t^e wh W otofT tain J ng 10 ° r l2 Per C6nt - ° f ^roXfc acid 

 when d ;L t * £' Calcare ° US l ma " er has bee » amoved, and then, 



of about 50 I J ! •« e ^T ed 7 dirCCt Hght With a linear P ™' 

 or about 50 the sihcified fibrous structure will be freouentlv found 



ma beautiful state of preservation, and when comj'S w h that of 



he recent sponge Halispon.ia ventriculoide*, the fibrous tissues of 



the two are so much alike as almost to induce a belief that they be 



long to the same species under different circumstances. 7 



i have two thin sections at right angles to the natural surfaces of 



a specimen of Mantell's Ventriculites radiatus from near the Stom 



of the cup embedded in flint; viewed by transmitted light 3a 



we S 7e i, fJZTn^V™^ P^/^ structural dLlc^ 

 we see m om recent Hahspongia ventriculoide*. There is the samp 



rnXuT lib' 6 f "T *"?* ** **"" 0M ^ % 

 arenulous and the internal secondary ones are destitute of sand and 



J j? Stro f Q ^y indicative of a close alliance, there are several fibres 

 projecting from the external surface terminated by a single grain of 

 and as in the recent sponges; and the external surface of the fossil 

 sponge is as abundantly arenulous as that of the recent one 



In Elhs and Solander's work there are neither generic nor specific 

 descriptions given of the sponges figured , and Espi copies El's and 

 Soknder s figures and designates the specimen n/sfro«£i a otaMUca 

 in". " 0t f e T \ that tl«s specific designation has any pretensTon to ' 

 stand ; and I have therefore named the species ventriculoides, as mo e 

 consistent with its ancient alliances, and as forming a bond of umon 

 with the very closely allied species of Mantell's Ventriculites radZus 

 Halispongia Mantelli, Bowerbank. (Plate XL VII figs 3&4 ) 

 Sponge cup-shaped, thin; pedicel short. Surface, outer one 

 smooth and even ; inner one furnished with depressed ridges, red™ 

 tmg from the bottom of the cup to the distal margin ; distal margin 

 attenuated. Dermis retiform, abundantly arenulous. Oscula simple 

 dispersed very minute inconspicuous. Pores dispersed, visibleby 

 the ad of a 2-inch lens. Skeleton-primary fibres abundantly 

 arenulous ; secondary fibres rarely arenulous. ouuuantiy 



Colour light ochreous yellow. 



