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XIV. Report on the Hydroida collected during the Expeditions of H.U.S. ‘Porcupine. 
By Professor G. J. Auuman, F.R.S. 
Read 18th February, 1873. 
[Puates LXV. to LXVIII.| 
THE Hydroids obtained during the two expeditions of the ‘ Porcupine’ (1869 and 
1870), and placed in my hands for determination, consist of trophosomes, in some 
cases destitute of gonosome, but in others provided with this important element of 
the colony. Nofree planoblasts are contained in the collections of either expedition. 
The dredgings of 1869 are, on the whole, from greater depths, and contain a greater 
number of new species than those of 1870; for though a few of the specimens of the 
expedition of 1869 are from inconsiderable depths (64, 75, and 90 fathoms), the majority 
are from very deep water, having been dredged from depths varying from upwards of 
100 to between 600 and 700 fathoms. The deepest dredgings of 1870 were from 539 
fathoms. 
One result of the expeditions has been the determination of the very extensive range 
of depth enjoyed by some well-known species. Thus Sertularella polyzonias, though 
very generally distributed in the zone between tide-marks, was brought up by the 
‘Porcupine’ explorers from a depth of 374 fathoms. Hydrallmania falcata, though a 
common species on the European shores of the Atlantic in the coralline zone of Forbes, 
which corresponds to a depth of between 15 and 50 fathoms, was obtained by the 
‘Porcupine’ explorers from a depth of 542 fathoms; while Thuiaria articulata was 
brought up from 632 fathoms, though frequenting a depth of less than 50 fathoms 
round our shores. 
Many species which have not yet been obtained elsewhere were brought up from 
great depths. Among these is a Diphasia from a depth of 632 fathoms; while a 
Plumularidan which must be referred to a new genus (Cladocarpus) was brought up by 
the same haul of the dredge. Two new species of Thuiaria were dredged from a depth 
of 640 fathoms, and a Lafoéa from 345 fathoms. A Sertularella nearly allied to 
S. Gayi, of which it may, perhaps, be regarded as only a variety, ranged from 290 to 
605 fathoms. It is a fact by no means without significance, that, in every case hitherto 
observed, these deep-water Hydroids belong to forms which produce fixed sporosacs 
instead of planoblasts. 
In the records of the expedition of 1869, it is stated that fragments of a Hydroid were 
VOL. VINI.—Part vill. April, 1874. 3U 
