188 
3-jointed, basal joint thick and pretty long, the two next joints thin and short, terminal seta 
short. Maxillule? — Maxille (fig. 3n) with smooth basal joint, second joint short and 
comparatively thick, third jot of average length with finely serrated inner margin. Maxil- 
lipeds (fig. 3n) proportionally rather below medium size, second joint longer than the third, 
terminal joint smooth. Peduncle of the natatory legs moderately broad. Abdomen much as 
in Mysidion, but the third segment is as long as the second. 
POST-LARVAL DEVELOPMENT. My observations and conclusions are stated 
in detail in the general part p. 54. 
HABITAT. In the diagnosis of the genus I have enumerated the different parts 
of the body to which the females may be seen attached. They have been found in all the 
northern species of the genus Hrythrops, viz. Er. erythrophthalmus (Goes) (= Er. Goésti G. O.8.), 
Ey. elegans G.O.8. (= Er. pygmeus G. O.8.), Er. microphthalmus G. O. 8., Er. serratus 
G.O.8. and Er. abyssorum G.O.S. About the depth in which these species live, and about 
the remainder of their biology, I refer the reader to the monograph by Sars. Most of my 
twenty-one infested specimens were without special locality, some specimens of Hr. serratus 
and Er. abyssorum were taken off Kvalé, one Er. erythrophthalmus off Tjoto. The parasites 
appear on adult males, on immature females and on females with marsupium, but in the 
latter the marsupium was either empty or filled with a parasite of the genus Mysidion. To 
show the occurrence of the parasites, I will give the following extract of my notes arranged 
according to the hosts. 
1. Er. erythrophthalmus (Goés). On a female from Tjoté in which the development 
of the marsupium had commenced, appeared a large parasite with fourteen ovisacs on the 
back of its second abdominal segment. _ 
2. Er. elegans G.O. 8. In a female whose marsupium was disturbed, occurred 
three parasites, two on the back of the second abdominal segment; one of these animals 
was nearly full-grown, the second somewhat smaller; the third, almost adult, female, was 
found on the back of the sixth abdominal segment near its posterior margin. On a female 
without marsupium were found altogether five females: one half-grown specimen on the upper 
side of the right eye, at the boundary between the cornea and the stalk; another somewhat 
smaller specimen on the inner side of the same eye-stalk; on the dorsal side of the carapace 
were two good-sized individuals, and a large one with three ovisacs, each containing only 
one egg, was attached to the second abdominal segment, at the centre of its dorsal side. 
3. Er. microphthalmus G.O.S. On a specimen with empty marsupium appeared 
a large female without eggs on the dorsal side of the last thoracic segment. In a female 
without marsupium was found a large parasite with six ovisacs on the dorsal side of the 
second abdominal segment. On a male I met with a large parasite with six ovisacs on the 
back of the first abdominal segment. 
4. Py. serratus G.O.S. In an adult male was seen a good-sized female on the 
upper side of the right eye close behind the cornea. In a female with marsupium containing 
