188 



3-jointed, basal joint thick and pretty long, the two next joints thin and short, terminal seta 

 short. Maxillnlae? — Maxillae (fig. 3n) with smooth basal joint, second joint short and 

 comparatively tliick, third joint 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 Erythrops, viz. Er. erythrophthalmns (Goes) (= Er. Goesii G-. 0. S.), 

 Er. elegans G. 0. S. (= Er. pygmmis G. 0. S.), Eh-, microphfhalmus G. 0. S., Er. serratus 

 G. 0. S. and Er. abyssorum G. 0. S. About the depth in which these species li\'e, 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 specimeriS of Er. serratus 

 and Er. abyssorum were taken oft' Kvalo, one Er. eryfkrophthalmus oft" 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 occun-ence of the parasites, I will give the following extract of my notes arranged 

 according to the hosts. 



1. Er. erythrophthahnus (Goes). On a female from Tjoto in which the development 

 of the marsupium had commenced, appeared a lai'ge parasite with fourteen ovisacs on the 

 back of its second abdominal segment. 



2. Er. elegans G. 0. S. 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 tliird, 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. 0. 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. Er. serratus G. 0. S. In an adult male was seen a good-sized female on the 

 upper side of the right eye close beliind the cornea. In a female with marsupium containing 



