40 Mr. H. J. Carter on the Spongida. 



Fossil Sponges. 



In a palasontological and geological point of view, it might 

 be assumed that all the orders of sponges to be hereafter men- 

 tioned existed as far back, at least, as the Upper Greensand 

 of the Cretaceous system, not only from the resemblance of 

 entire forms, but from actual identification of the spicules and 

 other elementary parts themselves. These, besides being found 

 in the powder of many hollow flints, exist at Haldon Hill, 

 near Exeter, promiscuously and abundantly in a distinct 

 stratum of fine sand — the former in direct connexion with 

 the fossilized sponge, and the latter in a drift-accumulation. 

 This has long been known ; and what I have stated re- 

 specting the representatives of the orders will be found in 

 the figures &c. of my paper on the subject, published in 

 the 'Annals' of 1871 (vol. vii. p. 112, pis. vii. to x. inclu- 

 sive). It is true that all the orders are not represented 

 by the bare spicules and fragments of glassy fibre therein 

 illustrated ; but sufficient, I think, to justify our assuming 

 that the others, which can only be recognized by a frag- 

 ment of the entire fibre respectively, may hereafter be found 

 in this very interesting, but very little worked, field of 

 discovery. 



What took place in the Cretaceous Period is taking place 

 at the present day, especially in the deep sea, as evidenced 

 by the " dredgings " of H.M.S. ' Porcupine,' which indicate, 

 through the specimens now with me, that about 100 miles 

 north of the Butt of Lewis, in 632 fathoms (station no. 57), 

 there must be a bed of sponge-spicules of many kinds, 

 portions of which are rounded by the currents into pebble- 

 like forms, which one day may become the nuclei of flints 

 or rounded portions of sandstone respectively, like those 

 now scattered over the Cretaceous area; while the bed it- 

 self may become, like that in the Upper Greensand of Haldon 

 Hill, a heterogeneous mass of sand and fossil sponge- 

 spicules. So also a recent specimen of the same " dredgings," 

 figured in the l Annals ' (1873, vol. xii. pi. i. figs. 1 & 2), con- 

 sisting, at least, of seven different sponges congregated together 

 in a very small space on a bunch of dead Loplwhelia, points 

 out how " the powder of hollow flints " is often found to con- 

 tain a heterogeneous mixture of spicules in addition to those 

 which belonged to the original sponge^ and thus defies all at- 

 tempts, in many instances, to specialize the latter. 



[To be continued.] 



