130 Mr. H. J. Carter on Fossil Sjjonge-spicules of 



a species of Geodia with tlie liextemate or furcate spicule of 

 Stelletta and the siliceous balls of a Geodia, in which case the 

 genera of Schmidt's groups of Ancorinida and Geodidin^ 

 would come together. 



Lastly, we come to the simple temate or trifid head of the 

 long-shafted spicules, of which three kinds at least, with their 

 varieties, abound in this deposit, viz. fig. 70, which is very- 

 stout, with long shaft and three arms expanded laterally, 

 almost horizontally, and a little recurved. In the illustration, 

 which is taken from the most perfect one that I coidd find, 

 the arm on the left side is broken off square, and the other 

 two, which were about equal in length, broken or rounded off 

 by attrition. Fig. 36, PI. IX., also belongs to the simple 

 temate division of the head with long shaft ; but the arms are 

 more or less straight, elongate, attenuated, and spread out at 

 equal distances from each other, somewhat forwards. Fig. 71 

 is another of this kind, but frequently with very little differ- 

 ence between the length of its shaft and the expanded arms. 



Of these the two foi-mer, viz. figs. 70 & 36, might, from the 

 length of their shafts, have belonged to the circumferential 

 spicular zones respectively of two different species of Geodia. 



But the prevalence of fig. 71 and its varieties, chiefly in 

 size, so nearly resemble the stout spicules with which an 

 existing species, viz. Dercitus niger (Annals, Jan. 1871), is 

 densely charged, that I do not think that a more appropriate 

 appellation can be assigned to it than that of Dercites lialdo- 

 nensis. 



The existing type grows on the rocks at Budleigh-Salterton, 

 and is a black variety of Hymeniacidon BiLcklandi, Bk.,= 

 Pachastrella Bucklandi, Sdt. 



We now leave the spicules of the ternate system, and go 

 to that large acerate fonn whose middle and ends are repre- 

 sented in PI. X. fig. 76, a a, which, with the exception of 

 Dercitus niger (which is peculiar in this respect), is the cha- 

 racteristic body-spicule of all the known Pachytragife ; and 

 lience its great abundance of different sizes in the Haldon 

 deposit is easily understood. It is smooth, acerate, fusiform, 

 and for the most part stout and slightly curved, as shown in 

 the figiu'e, which otherwise represents the average size of the 

 largest specimens. 



The same remarks apply to the acuate spicule, whose large 

 and small ends are given in fig. 77 «, but with this exception, 

 that the acuate form is somewhat smaller and less abundant 

 in the existing species as it is in the Ilaldon deposit. It seems 

 also to be but a modification of the body-spicule, in which one 

 half is shortened and enlarged at the expense of the length of 



