= 46 — 
blance in the spicules of the recent sponges and those from 
the Horstead flint. Beyond the differences in the state of 
preservation there is scarcely anything to distinguish the fossil 
Chalk spicules from those of the existing sponge, P. amyg- 
daloides which was dredged from a depth of 292 fathoms near 
Cape S" Vincent. 
Similar spicules, as regards form, have been found in 
the Irish Chalk (Wright: op. cit. Pl. II, fig. 7 a, b) in West- 
phalia (Ueber Coelop. Taf. V, figs. 54,' 55) and also in the 
Eocene Sand of Brussels (Rutot: op. cit. Pl. III, fig. 8). 
Pachastrella Carteri, n. sp. 
(Plate III, figs. 29, 30, 31). 
Simple quadrifid spicules, with short robust, cylindrical 
or conical, and obtusely rounded arms, forming a depressed 
pyramid with a short arm at the apex. Infigs. 29 and 31, the 
stout conical blunted arms vary from 0,47 mm. to 0,67 mm. in 
length, and are 0,225 mm. in thickness. In the more regular spicule 
(fig. 30) the arms are cylindrical and measure 0,337 mm. by 
0,112mm. These spicules appear intermediate between those forms 
ofskeleton spicule with long pointed simple arms of which P. amyg- 
daloides, Carter is the type, and those in which one or more of 
the arms are bifurcated at the extremities as in the recent 
sponge P. abyssz, O. Schmidt, and the fossil, P. przmoeva, 
Zittel. It is true that in both the recent and fossil Pacha- 
strellid sponges, various forms and sizes of quadrifid spicules 
are present in the same sponge, but as I have not noticed 
any sponges with spicules having the short, blunted arms of 
these examples, I think they may belong to a distinet species, 
which I propose to name in honour of Mr. H. J. Carter F. R. 5. 
Pachastrella primaeva? 
Zittel: Stud. iiber Foss. Spongien p. 100, Taf. XII, fig. 4. 
(Plate ILI, figs. 28, 32, 33, 34). 
Spicules with four unequal arms, straight or slightly 
