474 PROFESSOR G. J. ALLMAN ON THE HYDROIDA 
SERTULARID. 
DIPHASIA CORONIFERA. Plate LX VI. figs. 2, 2%. 
Trophosome.—Stem attaining a height of about three inches, simple (in specimen), 
stout, rigid, not fascicled, tapering towards the summit, pinnate; pinne alternate. 
Hydrothece tubular, with the margin entire, free for about the upper third, which 
diverges without any abrupt bending from the axis, each pair of hydrothece on the 
pinne separated from its neighbouring pairs by an interval of about half the length of 
the hydrotheca, but by about double that interval on the main stem. 
Gonosome.—Gonangia (male) springing from the pinne, each at a point just below 
a hydrotheca, contracted below into a short curved peduncle, rapidly expanding upwards, 
and terminating in a broad circular summit, whose circumference is raised into eight 
similar, strong, broad spines, and from whose centre projects a short papilliform process 
carrying the orifice on its extremity. Female gonangia not known. 
This species was dredged in lat. 64° 15’, long. 6° 15’, from a depth of 632 fathoms. 
SERTULARELLA GAYI, var. RoBUSTA. Plate LXVI. figs. 3, 3°. 
The form here recorded as a variety of Sertularella Gayi is a Hydroid with a strongly 
fascicled, thick, rigid stem, which attains a height of about six inches, and sends off on 
all sides simple, non-fascicled, obliquely jointed ramuli, and occasionally a fascicled 
branch, from which non-fascicled ramuli then proceed, as in the main stem. The 
hydrothece are borne one on each internode of the ramuli, immediately below a joint ; 
‘they arch outwards from the ramulus, are turgid below, marked upon the upper side by 
transverse ruge, smooth below, and have an obscurely four-toothed aperture. 
The gonangia (female ?) are ovate, on short peduncles, strongly annulated towards the 
summit, but smooth below; the summit is in the form of a saucer-shaped expansion, 
from the centre of which rises a conical process, carrying on its top an obscurely two- 
lobed orifice. 
If it were not for the occurrence of intermediate forms, I should have regarded the 
present Hydroid as specifically distinct from Sertularella Gayi. It differs from typical 
specimens of S. Gayi by the irregular disposition of its ramuli (which in the latter 
species are pinnate), and by the tubular summit of the gonangia. From S. polyzonias, 
with which S. Gayi is closely allied, it differs by its much more robust habit and thick 
fascicled stems. In specimens obtained from some other dredgings of the ‘ Porcupine,’ 
the ramification is rather more pinnate. It seems, indeed, to form a connecting link 
between S. polyzonias and S. Gayi, and would thus go far to justify us in regarding all 
three as merely varieties of a single species. 
The form here described would seem to be rather widely distributed over the area 
explored. It was obtained from the cold region, at depths of 345, 363, and 605 fathoms, 
with a bottom-temperature which varied from 31°-4 Fahr. to 29°'8 Fahr., while it was 
