Mr. H. J. Carter on known Fossil Sponges. 283 
kina (Zeitschrift f. wiss. Zool. 1880, Bd. xxxiv. Taf. xx.- 
XXil.). 
Next come the Creratina (Order II.), which, with the 
exception of the following order, viz. PSAMMONEMATA, appear 
to be by far the most abundant of all existing sponges, and at 
the same time may reach a very large size (ew. gr. the Luf- 
faria from the West-Indian seas, in the British Museum), 
whose kerataceous fibie is so thick and hard when dry that it 
breaks with the shining fracture of hard glue. 
This horn-like substance, which, as before stated, has lately 
received the name of “ spongin,” 1s in its elementary compo- 
sition so nearly allied to the chitin of the insect-skeleton that 
it seems strange that the latter should be handed down in a 
fossilized state (if such should be the case) and not the former. 
According to Krukenberg the elementary composition of 
spongin and chitin respectively is as follows :— 
Spongin........ C.30 H.46 N.9 O.18 
OL eee 15 26 2 10 
Thus (to me) the former is the densest and physically the 
most solid of the two, especially in Lugfaria. 
What the branched forms in the Quadersandstein of 
Saxony, called by their discoverer Geinitz ‘‘ Spongites saxont- 
cus,’ or the net-like figuration on the surface of crooked 
cylindrical bodies (‘ Lhizocorallium,” alluded to by Zittel, 
‘ Handbuch der Paleontologie,’ pp. 142, 143), may be remains 
to be decided. 
Again, thereisno mention of the PSAMMONEMATA (Order III.) 
in a tossilized state, although I found them in a recent one in 
such great abundance in the “ ridge” on the south-east coast 
of Arabia above alluded to—seeming to indicate in this in- 
stance the first step towards fossilization, if not also what 
would probably have taken place and been recognized in 
former tfossilizations if such had occurred. 
— My Dysidia antiqua trom the Carboniferous of Ayrshire 
(‘ Annals,’ 1878, vol. i. p. 189) has been relegated by Dr. 
Hinde to those kinds of sponges which come under my order 
HOLORHAPHIDOTA, by the generic name ot “ Hapliston”’ (Mon. 
Brit. Spong. Paleeontographical Society’s vol. tor 1887, pt. ii. 
p- 147, pt. 1. pl. v. figs. 2, 2 a). 
Of the RHAPHIDONEMATA, whose fibre is again corneous, 
J found a small branched fragment, apparently of a Chalina, 
having the usual form of acerate spicule presented by that 
family, in a detrital piece of chert from the remains of the 
Upper Greensand so abundant in this locality (Budleigh 
