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 (pi. XI, fig. 3 h, x). The head is provided with 

 well developed frontal and lateral borders. Antennulae short, 2-jointed. Antennae wanting. 

 Hairs of the mouth-border short, but distinct. Maxillulae and maxillse 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 maxillse or 

 lnaxillipeds. 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. Pig. 2 b in pi. 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. abyssomm), sometimes varying exceedingly in size (pi. XI, fig. 3 c), and 

 mutual pressure not unfrequently having caused their shape to become irregular and their 

 attachment difficult to discern (pi. XI, fig. 3a); frequently again, they are af about equal size, 

 of regular shape, and their attachment easy to observe (fig. 3 b). 



LARVA. It is known in both species, and on the whole only differs from the 

 species of Sphwronella living in Amphipoda by the shortness of the setae of the caudal 

 stylets, these setae 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. 0. Sars and Parerythrops Gr. 0. S. (family Mysidae, 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. 



