186 



Antennae wanting. Mouth middle-sized; mouth-border provided with very distinct hairs. 

 Maxillulse small, probably constructed like those of the female, and without additional branch. 

 Maxillae extremely large, the basal joint much compressed and veiy broad; the two last 

 joints, which are entirely fused, form a long and powerful, proximally somewhat curved, 

 distally almost straight joint. The basal joint of the maxillipeds somewhat smaller than in 

 most species of Sphferonella , second and third joints fused into one exceedingly short joint, 

 which has no spine at its distal inner angle; last joint slender, pointed, perceptibly longer 

 than the penultimate one. The sub-median skeleton without processes on its posterior part. 

 The trunk without legs and caudal stylets. (Fig. 3 k only shows one single, but exceptionally 

 large spermatotheca (q), but this no doubt is an anomaly in the specimen illustrated, 

 as in two other individuals I found, as usual, two much smaller and normally situated 

 spermatothecse. 



OVISACS. They are hinged to the lists of the genital apertures, sub-globular or 

 shortly pyriform, from scarcely middle-sized to small; their- number can amount to thirteen 

 or fomteen. Eggs of average size, not numerous. 



LARVA. Resembles in nearly all its features (fig. 3 m) the larvae of certain species 

 of Sphceronella parasitic on Amphipoda. The essential difierences found are as follows: the 

 second joint of the maxillae is short and comparatively thick (fig. 3n), the third joint is 

 finely serrated at its inner margin; the seta of the caudal stylets is short, not half the 

 length of the cephalothorax. 



POST-LARVAL DEVELOPMENT. The male comes out of the larva (fig. 3m) 

 directly, without any intermediate stage. Whether the female passes through the pupa stage 

 is not known, but it appears more probable to me that its development resembles that 

 of the male. 



HABITAT. The females live attached to the eye-stalks, the carapace, the back 

 and sides of the fi-ee thoracic segment and the six first abdominal segments of all species 

 of the genus Erythrops G. 0. Sars (order Mysidacea), in Norway. 



REMARKS. The genus comes very near to Mysidion, and the characters by 

 which both genera are distinguished from those previously described are stated in the 

 remarks about the last-mentioned genus. From the latter the female differs in the lack of 

 maxillipeds, in the tolerably short distance between the genital apertures, in the ring by which 

 each of these apertures is surrounded , and by the two conspicuous chitinous knots above 

 the receptaculum seminis. The male deviates both from Mysidion and from all other genera 

 in the minute size of the antennulse and in the smallness of the distal part of the maxillipeds. 

 And tills genus deviates from all other forms by living attached to the outside of the fi-ee 

 surface of its hosts. — The whole of my large material collected by Prof G. 0. Sars I have 

 referred to one species; the subsequent remarks about this parasite will form a supplement 

 to the above account of the type. 



