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tioii of a very large material of Danish species of the genus Mysis Latr. (sens. Sars in 

 1879), and of Macropsis Slabberi (v. Ben.), as well as of a number of specimens of Gastro- 

 saccus Norm. — all shallow water species, — gave a negative result, neither did I find any 

 parasite on numerous specimens of a species of Mysidae taken in shallow water in the West- 

 Indies, nor on a great number of specimens belonging to two pelagic species of the genus 

 Siriella Dana. In Cuniacea I have found altogether five species of the genus SpJueroneUa 

 on six species belonging to the genera Diasfylis Say, Eudorella Norm, and IpMnoe Sp. 

 Bate, which three genera belong each to one of the eight families established by G. O. Sars, 

 whereas an investigation of numerous other species, among which a very large material of 

 several species which were taken in Denmark in very considerable quantity, as Ciima scor- 

 pioides (Mont.), Lamprops fasciafa (i. O. Sars, Leucon nasicus Kr. Leucon nasicoides Lilljbg., 

 Leucon acutirostris G. 0. Sars, Eudorellopsis deformis (Kr.) Diastylis resima (Kr.) and 

 Leptostylis ampuUacea (Lilljbg.), gave a negative result. Witliin the order Isopoda, these 

 parasites — altogether three species of the genus SphceroneUa — are only found in two 

 species of the genus Janira Leach and in Munnopsis typica M. Sars, all thi'ee forms 

 belonging to the large tribe Asellota, whereas an investigation of numerous forms belonging 

 to other families, among which some species of Idothea F., Astacilla Cordiner, and Gnathia 

 Leach, were represented by a great number of specimens, gave no result. (Of the small 

 order Tanaidacea I have examined a good number of specimens from Denmark and numerous 

 specimens of several species from Sicily, without finding a single parasite). The chief 

 quantity of the parasites, namely twenty-eight species (the genus Stenothocheres and about 

 three quarters of the genus SphceroneUa], were found on Amphipoda, and witliin this oi-der 

 exclusively on Gammaridea (on twenty-eight species). An inspection of a great number of 

 specimens of different species of Caprellidae and of some specimens of Cyamidae gave no 

 result. (Among the material from the »Ingolf« expedition I found in 18!t5 on an ^gina 

 Kr. a species, wliich will be described in the report on the results of this expedition). Of 

 Hyperiidea I have only examined a few species. In giving a short general view of the 

 occurrence of the parasites within the Gammaridea-group, I will avail myself of the twenty- 

 five families adopted by G. 0. Sars in his new important work: ^>An Account of the Cru- 

 stacea of Norway, Vol. I, Amphipoda"^ ; they are found in one or more representatives of 

 the following fourteen families: Pontoporeiidse (the genera Bathyporeia Lindstr. and Aryissa 

 Boeck), Ampeliscidse (the genus Ampelisca Kr.), Amphilochidae (the genera Astyra Boeck, 

 Amphilochoides G. O. Sars and Gitanopsis G. 0. Sars), Stenothoidaj (the genera Stenothoe Dana 

 and Meiopa Boeck), Oediceridae (the genus Perioculodes G. 0. Sars), Parampliithoids (the genus 

 Faramphithoe Bruz.), Epimeridse (the genus Acanthozone Boeck), Syrrhoidas (the genus Bruselia 

 Boeck), Calliopiidse (the genus Gulliopius Lilljbg.), Atylidae (the genus Farutylus G. O. Sars), 

 Gammaridae (the genus Cheirocratus Norm.), Photidse (the genera Lemhoides Stebb., Frotomedeia 

 Kr., Leptocheirus Zadd., Gammaropsis Lilljbg. and Microprotopus Norm.), Corophiidse (the genus 

 Corophium Latr.) and Dulichiidse (the genus Dulichia Kr.). Of the lemaining eleven families the 



