NARRATIVE OE THE CRUISE. 
751 
Radiolarians and Diatom frustules made up a very large part of 
the deposit, probably about one fourth of the whole. 
It would take up too much space to give the list of new fishes 
and invertebrates from this trawling ; nineteen specimens of the 
former and about one hundred specimens of the latter were ob- 
tained, most of the species being new ones first discovered by the 
Expedition. Among the most remarkable were the four specimens 
of Monocaulus, referred to by Professor G. J. Allman, F.R.S., in 
the following notes on the Hydroida collected during the cruise, 
the first part of whose Report 1 has been published : — 
The Hydroida. — “ The only group the investigation of which 
has yet been completed is that of the Plumularidse, which contains a 
large number of new forms, no fewer than eight being peculiar 
types, which have rendered necessary the construction of as many 
new genera ; while the number of species now for the first time 
determined amounts to thirty-one. 
“Among the new genera Streptocaidus (fig. 264), dredged off 
Porto Praya, San Iago, from a depth of 100 fathoms, presents a 
form of ramification hitherto unknown among the Hydroida, the 
ultimate ramuli or hydrocladia being thrown by the twisting of 
the stem into a graceful and beautiful spiral; while in Diplocheilus, 
dredged in Bass Strait from a depth of 30 to 40 fathoms, the 
curious duplication of the hydrothecal margin is as remarkable as 
it is unique. Several new forms, the special interest of which 
consists in their presenting transitional characters between certain 
well-marked Plumularian groups, have also been obtained. 
4 ■ A striking feature among the Plumularidse brought home 
by the Challenger is the large proportion of species having open 
phylactocarps, as seen in the types of Acanthocladium, Lyto- 
carpus, and Cladocarpus. These, by the analysis they present of 
the more usual form of phylactocarp as shown in the corbula of 
Aglaophenia, are of special interest in throwing light on the 
morphology of the structures which in the phylactocarpal genera 
are adapted to the protection of the gonangia, and in the con- 
firmation they afford of the conclusion that the essential parts of 
these structures are to be regarded as greatly developed and 
peculiarly modified nematophores. 
1 Report on the Hydroida — The Plumularidse, Zool. Chall Exp., part xx., 1883. 
Fig. 264. — Streptocaulus pulcher- 
rimus, Allman ; nat. size. 
95 
(narr. chall. exp. — vol. i. — 1885.) 
