RECEPTACULITES. 139 



17. Receptaoulites Neptttni, Defrance. Plate II, fig. 3, and Plate IV, fig. 1. 



1827. Eeceptaculites Neptuni, Defrance. Diet, des Sciences Nat., vol. xlv, 



p. 5, Atlas, pi. lxviii, figs, la, lb, 

 lc,ld. 

 1826-33. Coscinopoea placenta et sulcata, Goldfuss. Petref. Germ., Th. 1, 



p. 31, pi. xix, figs. 18, 19. 

 1842. Eeceptaculites Neptuni, Archiac and Verneuil. Trans. Geol. Soc, ser. ii, 



pt. 2, p. 407. 

 1844. — — F. Roenier. Ehein. Uebergangsgeb., p. 59. 



1852. — — Quenstedt. Handb. d. Petref., p. 670, pi. lx, 



fig. 18. 

 1868. — — Dames. Zeitscb. d. deutsch. geol. G-esellsch., 



Bd. xx, p. 483, pi. x, fig. 1. 

 1875. — — Gurnbel. Beitrage Abbandl. d. k. bay. Akad. 



der Wiss., CI. ii, Bd. xii, Ab. 1, 

 p. 169, pi. a. 

 1878. — — Quenstedt. Petref. Deutscbl., Bd. v, p. 596, 



pi. 142, fig. 20. 



1878. — sctphioides, Quenstedt. Idem., p. 586, p. 142, figs. 15, 16. 



1879. — Neptuni, Nicholson. Man. Pal., vol. i, p. 127, fig. 29. 

 1876-80. — — Zittel. Handb. d. Pal., p. 84, fig. 20. 



1880. — — F. Roenier. Letbaea pal., vol. i, p. 290, Atlas, 



pi. xxxv, figs. 7 a, b, c. 

 1882. — — T. R. Jones. Cat. Foss. Poram. Brit. Mus., 



p. 4. 



1884. — — Hinde. Quart. Journ. Geol. Soc, vol. xl, p. 841. 



1885. — — Vosmaer. Porifera. Bronn's Klassen u. Ord- 



nungen d. Tbier-Eeicbs, Bd. ii, 

 p. 275. 



Sponges varying in form from flattened discs with a circular outline, to open 

 cups, and ranging from 65 to 180 mm. in diameter. The walls, as a rule, gradu- 

 ally increase in thickness, from the conical nucleus, where they are about 3 mm. 

 in thickness, towards the margin of the disc or cup, where they attain a thickness 

 of 10 to 15 mm., and in one exceptional example 20 mm. 



The rhomboidal spicular plates of the outer or under surface of the Sponge- 

 wall are usually flat, though in some specimens they become concave through 

 pressure ; their edges are thin and usually crenulated beneath. They vary from 

 4 to 5*5 mm. in width. They are disposed so that a linear interspace exists 

 between adjoining plates, which is shown by the curved decussating ridges in the 

 casts of the outer surface. The transverse or horizontal spicular rays are conical, 

 from 1 mm. to 1*5 in thickness; they usually extend beyond the respective head- 



