the Greensand compared loith those of existing Sj^ecies. 129 



of their like, wliicli exist in countless myriads scattered through- 

 out the deposit.) The figures, then, to which I have just 

 alluded are very similar in character, and, together with the 

 vase-like trifid heads, figs. 61 & 67, and the bifid ones, figs. 65 

 and 64, may all be varieties of their proper types respectively, 

 produced in one species of sponge, to which I would give the 

 name collectively of Geodites haldonensis, taking fig. 58 as 

 the best representative of this group. 



If, then, we make this a Geodia^ it involves the addition of 

 an anchor-headed spicule with extremely long shaft (as those 

 know who have studied the existing species) ; and this we 

 appear to have in figs. 62 & 63, which, although slightly dif- 

 fering in form, may be but varieties of one tyjje ; also a large 

 smooth acerate spicule, like that of fig. 76 : and thus we have 

 all the spicular forms characteristic of the circumferential zone 

 of a Geodia, viz. : — (1) the thick ternate head, characteristically 

 furcated and vasiform in this instance ; (2) the vasiform, trifid, 

 extended head ; (3) the anchor-like or trifid recurved head ; 

 and (4) the large acerate spicule. Add, further, to these the 

 globular crystalloid or little siliceous ball (PI. IX. figs. 55 & 

 56) (found abundantly in this deposit) for the crust, together 

 with the large acerate and acuate spicules (figs. 76 & 77, PI. X.) 

 for the interior, and we have, with the exception of the minute 

 stellates &c. (also usually found in the existing species of the 

 Geodida3, but which, for reasons above given, we cannot ex- 

 pect to find in this deposit), all the spicular combination which 

 belongs to a Geodia, except that, I think, there is no existing 

 species known in which the arms of the ternate head are 

 furcated and also spread forwards, instead of horizontally and 

 more or less recurved. 



Such a condition may be seen, so far as the furcation goes, 

 in Schmidt's Stellettce and AncorincB (Spong. Adriat. Meeres, 

 Taf. 3 & 4, 1862) ; but here, again, the bifurcations are not 

 prolonged, but recurved. 



Fig. 69, which is hexternate, is, witli its varieties, also a 

 very common form in this deposit ; and here the arms are 

 spread out horizontally or laterally, and the furcations some- 

 what recurved, as in Stelletta &c. For this and its like, then, 

 I would propose the name of Stellettites haldonensis ; albeit 

 it is not certain that this spicule, too, might not have been 

 connected with a crust of siliceous balls and a spicular combi- 

 nation in other respects like that just mentioned, when it 

 would become a Geodites^ the absence of the siliceous balls 

 being Schmidt's distinction. But, then, his Stelletta discophora 

 has a crust of little siliceous disks, which are but a more de- 

 pressed form of the siliceous balls ; and so the future may furnish 



