178 
partly covered with the gluey substance, by which the female is attached to the inside of the 
marsupium, and it seems as if in these cases the animal had got its head irregularly covered 
with glue just after this substance had been secreted and before its becoming stiff (dry). 
MALE. This sex is known in both species. The body is short and clumsy. On 
the dorsal side of the head, somewhat in front of the hair-coat and at some distance from 
the median line, we see a knot or short cone (pl. XI, fig. 3h, x). The head is provided with 
well developed frontal and lateral borders. Antennule short, 2-jomted. Antenne wanting. 
Hairs of the mouth-border short, but distinct. Maxillule and maxille as in the female. 
Maxillipeds rather anomalous: their basal joint curved, at least with one good-sized, thick 
process on the outer side of its distal end; second and third joints coalescent, the terminal 
joint conical. The sub-median skeleton without processes at the base of either maxilla or 
maxillipeds. The trunk hairy; trunk-legs and caudal stylets wanting. The frontal thread 
furnished with peculiar expansions. 
OVISACS. ‘Typically they are shortly pyriform and attached to the lips of the 
genital aperture by a fairly short stalk. Fig. 2b in pl. XII shows the genital aperture (g), 
the lips of which are covered with a stiffened secretion, which, besides, forms a pretty large 
plate (h) covering the hindmost end of the semicircular list and the skin nearest to it; from 
this plate proceed numerous, distally thickening threads, which are cut off in the drawing 
(i); they are the stalks of the ovisacs, so the plate must be understood as being the coales- 
cent basal parts of these stalks. The ovisacs are numerous, twelve, fourteen, seventeen, or 
even more (see Mys. abyssorum), sometimes varying exceedingly in size (pl. XI, fig. 3c), and 
mutual pressure not unfrequently having caused their shape to become irregular and their 
attachment difficult to discern (pl. XI, fig. 3a); frequently again, they are af about equal size, 
of regular shape, and their attachment easy to observe (fig. 3b). 
LARVA. It is known in both species, and on the whole only differs from the 
species of Spheronella living in Amphipoda by the shortness of the sete of the caudal 
stylets, these sete being not nearly half as long as the cephalothorax. 
POST-LARVAL DEVELOPMENT. Is partly known in one of the species, and 
the stages known, which are very remarkable, are described in detail above on p. 61—63. 
HABITAT. In the marsupium of species belonging to the genera Erythrops 
G. O. Sars and Parerythrops G.O.S. (family Myside, order Mysidacea) from Norway. 
REMARKS. ‘This genus is admirably distinguished from the three preceding genera 
by the following characters: the genital apertures in the female are placed far apart from 
each other and from the odd receptaculum seminis, each has a skeleton of its own, finally, 
the ovisacs are attached to the lips of the genital apertures. In the three last characters 
it agrees with the following genus, but in the latter the female lacks maxillipeds, the genital 
apertures are much closer to each other etc. The males differ from all the preceding genera 
and agree with the following in possessing the two dorsal knots on its head. The meta- 
morphosis deviates very strongly from anything else I have observed of this kind. 
