Sponges from the Atlantic Ocean. 459 



represent a distinct sponge. I might also add that in no sponge 

 have I ever seen these tortuous acerates grouped together as 

 above described below the surface, excej^t in HymerapMa 

 vermiculata, Bk., and its variety erecta (PL XV. fig. 26, 5), 

 where their great inferiority in size and their forming part of 

 a distinct structure, from the midst of which projects large 

 acuates, shows at once that they are not Ophiraphidites tor- 

 tuosus. At the same time, as the laminiform species, viz. Hy- 

 merapMa vermiculata, Bk., grows on the surface of hard 

 objects, such as pebbles, and other sponges, indiscriminately, 

 and there are tortuous acuates mixed up with the tortuous 

 acerates in OpMvaphidites^ it may still be a question whether 

 this may not be after all a transformation of the spicules of 

 H. vermicnlata with which a few of the trifids of Pachastrella 

 abyssi have become accidentally mixed. 



Be this, however, as it may, after having described Oplii- 

 raphidites tortuosus as part of the dredgings of the ' Porcupine,' 

 the great point of interest that attaches to them is that such 

 spicules are found fossilized in the Upper Greensand of Haldon 

 liill, near Exeter, in the Mid-Miocene or Bruxellien " etage " 

 about Brussels, and in the Cretaceous strata of Westphalia, 

 in Germany, respectively. In my illustrations of the fossil 

 sponge-spicules of the Upper Greensand of Haldon Hill, near 

 Exeter, I have figured one ('Annals,' 1871, vol. vii. p. 131, 

 pi, X. fig. 79) under the name of ^^Esperites giganteus^'' con- 

 ceiving it then to be, from its sigmoid shape, a gigantic S- 

 shaped bihamate (fibula) of an Esperia^ whereas now I see 

 that it is a spicule like those of OpMrophidites tortuosus ; hence 

 the term ^^Esperites giganteus " should be erased, and that of 

 Opldraphidites tortuosus substituted for it. The specific name 

 ^^ giganteus " cannot be retained, because its size corresponds 

 with that of the spicules of the existing OpMrapMdites. I 

 next observed it in M. A. Rutot's illustrations of fossil sponge- 

 spicules " de I'etage Bruxellien " about Brussels (Ann. de la 

 Soc. Malacologique de Belgique, t. ix. 1874, pi. 3. figs. 5 & 29), 

 confirmed by its presence in some of the spiculiferous sand it- 

 self (kindly sent to me by M. E. Vanden Broeck), wherein it is 

 ])lentifully present ; lastly, in Prof. K. A. Zittel's illustrations 

 of sponge-spicules found about a specimen of Godoptychium 

 agaricoides from the Quadersandstein of Westphalia (Abhand- 

 lungen der k. bayer. Akad. der W. ii. CI. xii. Bd. iii. Abth. 

 Taf. 4. figs. 25 & 26, 1876). Schmidt has also figured them 

 (Grundz. Spongienf. d. atlant. Gebietes, 1870, p. 24, Taf. iii. 

 fig. 3, c), in connexion with CoraUistes Bov^erhankii [C. typus, 

 Sdt.), as they certainly are no part of this sponge. To M. 

 Rutot and Prof. Zittel I am greatly indebted for a copy of 



31* 



