26 
W. M. TATTERSALL. 
of tlie basal joint without set*, but armed with twenty-one stout spines increasing in 
size posteriorly. 
Length of adult and ovigerous female, 20 mm. from the eyes to the tip of the 
telson. 
Colour of preserved specimens light brown, with a broad band of dark brown 
pigment across the dorsal surface of the first segment of the pleon and scattered 
patches of dark pigment on the lateral parts of the carapace, basal joints of the 
antennules and antennae and the basal membranous pad of the eyes. 
One of the specimens has young, considerably advanced in development, in the 
incubatory lamellae. 
In both specimens the telson is considerably damaged, and the description and 
figures have been drawn up from both specimens and fragments of the telsons found 
along with them. This fact must be borne in mind in dealing with specimens of this 
species which may be found by future expeditions. It was a matter of considerable 
surprise and no little interest to find in this collection two specimens belonging to 
a genus hitherto known only from a single specimen from Greenland and two taken 
off the cost of Ireland. 
There can be no doubt that H. antarctica is co-generic with II. fyllse (Hansen, 
1887). All the distinctive characters of generic importance in the mouth parts and 
thoracic limbs of the latter are reproduced in II. antarctica down to the minutest 
detail. The points of difference between the two species are, however, sufficiently 
well-marked and numerous enough to justify specific separation. They may be pointed 
out as follows :— 
H. antarctica is in general build a more robust and less fragile species than 
II. fyllse. 
Antennse. —In II. fyllse the terminal joint of the peduncle is longer than the 
penultimate, whereas in II. antarctica the reverse obtains. 
Antennal scale. —In II. fyllse the outer margin bears only five spines, between 
which are numerous set*. In II. antarctica, on the other hand, there are eleven spines 
on the outer margin and no set* between them. 
Telson. —The telson in Hansen’s type-specimen was broken, but so much of 
it as remained showed that the armature consisted of both spines and set*. In 
H. antarctica the telson is armed with spines only, which are probably more numerous 
than in II. fyllse. The shape of the telson in both species is also somewhat divergent. 
That of II. antarctica recalls rather markedly the telson of Petalophthalmus armiger as 
figured by Sars in the ‘ Challenger ’ Report. 
Outer uropods. — II. fyllce has the outer uropods armed with both spines and 
set*, whereas in II. antarctica there are spines only present. The spines in II fyllce 
number six, while in II. antarctica there are twenty-one. 
Pleopods. —The type specimen of II. fyllce had only one pleopod remaining. This 
was one of the third pair, and is described by Hansen as biarticulate. Presumably, 
