212 BRITISH JURASSIC SPONGES. 
Distribution.—Corallian ; Lower Calcareous Grit; zone of Ammonites perar- 
matus, Scarborough (Coll. York Museum); Coral Rag, Settrington, Yorkshire. 
(Coll. W. H. Hudleston). 
Detached spicules, some of which may belong to this species though no 
connected specimens have as yet been found in the same beds, occur in the Coral 
Rag, North Grimston, Yorkshire (W. H. Hudleston), and on nearly the same 
horizon at Sturminster Newton, Dorsetshire, and at Hilmarton, near Colne, 
Wiltshire. (F. J. Blake.) 
Sus-orper.—MONACTINELLIDA. 
Family.—Sronaiuipa. 
Sponges inhabiting fresh water, with skeletons of acerate or cylindrical 
spicules and gemmulz or statoblasts furnished with small amphidise spicules or 
spined acerates differing from those of the skeleton. This family is very widely 
distributed geographically, but very rarely occurs in the fossil condition. 
Genus.—SponGinta, Lamarck. 
1815. Animaux sans vertébres, tom. ii, p. 98. 
The skeletal spicules are spined or smooth acerates. The gemmules are 
globular and covered with a layer of minute, spined acerate spicules, disposed 
tangentially. 
20. SponcintaA PuRBEOKENSIS, Young. Plate XIII, figs. 6, 6 a. 
1878. Sponeria PurBecKensis, Young. Geol. Mag., dec. ii, vol. v, p. 220, fig. d. 
1883. — — Hinde. Cat. Foss. Sponges, p. 21, pl. i, fig. 9. 
The only remains of this species yet known are masses of detached spicules 
preserved in nodules of chert, in association with valves of Cypris and other fresh- 
water organisms. ‘The spicules are exceedingly numerous, so as to constitute the 
main portion of the chert in which they occur ; they are slightly curved acerates, 
smooth usually, but Mr. Young has noted some which are minutely spined ; they 
have an average length of :37 mm., the longest measured are ‘415 mm. and from 
‘02mm. to ‘03 mm. in thickness. In some the axial canal is visible. The spicules 
