REPORT ON THE HYDROIDA. 
lvii 
The Challenger dredgings have yielded two new species of the singular Campanularian 
genus, Hypanthea. One of these comes from the Kerguelen region, where a species of the 
same genus had already been discovered by the Transit of Venus Expedition. The other 
is from the Falkland Islands in the Fuegian Region. Hypanthea is a comparatively 
shallow water form, inhabiting a bathymetrical zone which corresponds pretty closely 
with the Laminarian zone of the British coast. The species from Kerguelen, Hypanthea 
aggregata , came from a depth of from 10 to 60 fathoms, and the Fuegian species, 
Hypanthea hemispherica, from a depth of 12 fathoms. No example of Hypanthea has 
as yet been found outside of these two Regions. In both it covered the fronds of a 
Laminaria-like seaweed and was associated with Ohelia geniculata, thus pointing to an 
interesting parallelism between the Hydroid faunas of Kerguelen and the Falkland 
Islands, two Regions which, though separated by a wide distance in longitude, lie nearly 
in the same parallel of latitude. 
Our knowledge of the remarkable Perisiphonic genus, Cryptolaria, has been enriched 
by the discovery of eight species, all of which are new r . The maximum development of 
the genus as it appears in the Challenger collection is in the Australian and East Indian 
Regions, from which three species out of the eight have been obtained. These are 
Cryptolaria aby.ssicola from a depth of 2600 fathoms, Cryptolaria geniculata from a 
depth of 315 fathoms, and Cryptolaria gracilis from a depth of 700 fathoms. The 
remaining five are more sporadic in their distribution, being dispersed among five Regions, 
with one species in each, namely, Cryptolaria humilis, Azoric, with a depth of 1000 
fathoms ; Cryptolaria jlabellum, West Indian, with a depth of 390 fathoms ; Cryptolaria 
diffusa, Sargassic, with a depth of 2500 fathoms; Cryptolaria crassicaulis, Cape of 
Good Hope, with a depth of 420 fathoms ; and Cryptolaria pulchella, North Pacific, 
with a depth of 20 to 40 fathoms. 
The Lmited States exploration of the Gulf Stream, however, has shown that there 
is a large development of the genus in the West Indian Region, four species having 
been dredged during that exploration in the Gulf of Mexico. As far as we know at 
present, therefore, there are two centres of maximum development for Cryptolaria, an 
eastern centre in the East Indian and Australian Seas, and a western centre in the seas 
around the West Indian Islands, a phenomenon which, as we shall presently see, is also 
apparent in the distribution of the Plumularinse. 
The bathymetrical range of the various species show's further that Cryptolaria is 
essentially a deep-w r ater genus. Among all the species brought home by the Challenger, 
only one, Cryptolaria 'pulchella, has been obtained from a depth under 315 fathoms. 
This comparatively shallow-water species has been dredged from a depth of 20 to 40 
fathoms in the North Pacific, while four have been obtained from the great depths of 
700, 1000, 2500, and 2600 fathoms respectively. Among those, for the knowledge of 
which we are indebted to the United States expedition, three have been dredged from 
(zool. chall. exp. — pabt lxx. — 1888.) Aaaa li 
