264 
THE VOYAGE OF H.M.S. CHALLENGER. 
The casts of Foraminifera in glauconite and other silicates are especially abundant in 
some teiTigenous deposits, and will be specially referred to when discussing the chemical 
deposits in Chapter VI. 
Sponge Spicules. — The spicules of calcareous Sponges (Calcarea) are occasionally met 
with in the deposits, but they are rare and only locally present.^ 
Corals. — All the groups of the Coelenterata which secrete carbonate of lime contribute 
to the formation of marine deposits. In the neighbourhood of coral reefs the remains 
of Madreporaria and Hydrocorallinae may frequently make up the principal part of Coral 
Sands and Muds, and their fragments may be carried into the surrounding deep water. 
Certain species of Stylasteridae, Flahellum, &c., are inhabitants of deep water, and may 
be detected in deposits of all depths, but they never form a large part of a deep-sea 
formation.- 
Alcyonaiian Spicules. — These spicules are very frequently observed when examining 
the deposits from shallow water, and occasionally are present in considerable abundance 
in Globigerina or Pteropod Oozes. When they are locally abundant in deep water, as at 
Station 182,® it would seem as if some specimens of Alcyonaria had lived at the spot 
where the sounding w^as taken.^ 
Annelida. — The calcareous tubes of the Serpulidae in some coral reef regions, as 
for instance at Bermuda, form very massive structures,® and these tubes with their 
broken-down fragments can be recognised in nearly all marine deposits down to depths of 
300 fathoms. A few species live in very deep water, and fragments of their tubes are 
sometimes observed in the Red Clays, Globigerina Oozes, and in other kinds of pelagic 
deposits.® 
Crustacea. — When w’e remember the enormous numbers of Crustacea inh abiting 
all parts of tlic ocean, it is somewhat remarkable that their remains are so rarely met 
with in marine deposits. Chitin, which enters largely into the composition of the 
crustacean exoskeleton, is well known to be dissolved only with difl&culty in acids or 
alkalies, and it might be supposed that it would protect the calcareous portions of the 
skeleton from solution in sea-water. The disappearance of the crustacean exoskeleton in 
all likelihood arises from its areolar structure, which admits of relatively rapid solution 
after the death of the animal, and the putrefaction of its soft parts. 
In two or three cases the tip of a claw has been observed in the dredgings from both 
shallow and deep water, but with these exceptions, the remains of all the higher groups 
* See Pol^'jaeff, Report on the Calcarea, Zool. Chall. Exp., pt. 24. 
* See Moseley, Report on the Corals, ZooL Chall. Exp., pt. 7. 
* See p. 91, Chapter II. 
* Sec W' right and Studer, Report on the Alcyonaria, Zool. Chall. Exp., pts. 64 and 81. 
* See Murray, Proc. Iloy. Hoc. Edin., vol. x. p. 612, 1880, 
* M'Intcwh says : — Serpula philippeiuis reaches 1050 fathoms, a Vermilia 1450 fathoms, Placostegus challmgeriee 2375 
fsthoms, Placotteyut omatuM 29<X) fathoms, and Placostegus benthalianus the still greater depth of 3125 fathoms (see 
M'lntosh, RejKJit on the Annelida, Zool. Chall. Exp., pt 34, p. 508). 
