the Greensand compared with those of existing Species. 119 



posed to the beating of the most tempestuous seas. Hence 

 we shall not be sui-prised to find representatives of these in the 

 Haldon deposit. 



They will be found in Plates IX. and X. figs. 32-37 and 

 59-74 respectively. 



Some of the hexternate heads, as figs. 30, 31, and 33, might 

 either have belonged to Schmidt's Ancorinidte, in which are 

 included Stelletta &c. (Atlant. Spong. Faun.), or to the peri- 

 phery of the Dactylocalycida? (see Dr. Bowerbank's figures of 

 D. Masoni and D. Bowerhankii, 2, 3, and 6 respectively, Proc. 

 cit. 1869, pi. vi.); for they all have such hexternate heads for 

 their periphery, although those of the DactylocalycidjB appear 

 to be the thickest and to have the stoutest shafts, which, in 

 the fossil species are, for the most part, unfortimately broken 

 off. 



Where, however, the heads have not been so expanded, 

 although still in-egularly hexternate (as in PI. X.), the shafts 

 have consequently become more developed, and therefore have 

 partly remained, thus giving us facsimiles of the spicules 

 Avliich characterize the Pachytragiae generally, — that is to say, 

 Schmidt's Ancorinidge and Geodidinge (Atlant. Spong. Faun.). 



The figures 37-39 and 72-74 inclusively all appertain to a 

 quadi'ifid or quaternate system, which, whether belonging to 

 the Coralliospongia3 or to the Pachytragite, only find their pa- 

 rallel now, so far as I am aware, in Hyalonema {Carteria, 

 Gray), where the minute feathered spicules have the like heads 

 in miniature — some of the large ones with more extended 

 arms also — and all the long large ones a crucial branching of 

 the axial canal, with more or less inflation in the centre. 



In Ashonema setuhalense^ Kent, a similar condition exists ; 

 but here the minute spicules are hexradiate, and the large long 

 ones present a hexradiate cross, with more or less central in- 

 flation. It is almost impossible to see all six arms of the cross 

 at the same time in the long spicules ; but the quadrilohate 

 form of the inflation in many, if not most, is satisfactory 

 evidence of this condition when the cross is not otherwise 

 visible. 



Returning to the Pachytragia^, we find that the temate spi- 

 cules of the circumference, in the absence of silicified fibre for 

 support, are accompanied by strong acerate, fusiform, smooth, 

 and, generally, slightly curved spicules, which not only abound 

 in the interior, crossing each other in all directions to form the 

 skeleton, but frequently project somewhat beyond the surface 

 in connexion with the peripheral spicules — also that this form 

 is often accompanied by strong acuate spicules of the same 

 kind, in which one half of the spicule seems to be more or 



