398 On Gammarns campylops, Leach. 



published 1850, follows Samouelle's ' Entomologist's Useful 

 Compendium' in calling it camptolops. Milne-Edwards, in 

 Ann. Sci. Nat. vol. xx. (1830) p. 367, has camphyhps. 

 Its next appearance of any importance is in Spence Bate's 

 ' Catalogue of Amphipodous Crustacea in the Brit. Mus.' 

 (1862) as camptolops, hnt the same author in 1863 (Bate & 

 Westwood, ' Brit. Sess.-eyed Crust.') calls it campylops, at 

 which it remained till the revival of camylops in ' Das Tier- 

 reich' (1906). 



The confusion in regard to the description of the animal 

 has been even greater, and for this Leach himself was largely 

 responsible. His first notice gives practically no description 

 by which the species could be recognized, except the S-like 

 eyes. In the Trans. Linn. Soc. /. c. he divides the genus 

 Gammarus as follows : — 



A. Cauda sty lis geminatis superioribus stylo supero brevissimo 

 {i. e. Upper^ or inner, ramus of the third uropods very short). 



Spec. 1. Gammarus aquaticus. 



Gammarus pulex, Leach, Edin. Encycl. vii. 402-32. 



Habitat in rivulis et stagnis vulgatissima. 



Spec. 2. Gammarus marixus. 



Habitat in Danmoniae australis mari. 



B. Cauda stylis geminatis superioribus stylis subsequalibus 

 {i. e.'Rami of the third uropods subequal). 



Spec. 3. Gammarus Locusta. 

 G. oculis hiuatis. 



Cancer Gammarus Locusta, Montagu, Linn, Trans, ix. 92. 

 Habitat In Britauniae mari vulgatissime. 



Spec. 4. Gammarus campylops. 

 G. oculis flexuosis. 



Gammarus campylaps (sic), Leach, Edin. Encycl. \n. 403. 

 Habitat in mari prope Loch-Ranza in Arran Lisula. 



There is clearly something wrong here : G. aquaticus (now 

 called G. pulex) , which, as the common freshwater species, 

 cannot be mistaken, has the rami of the third uropods at least 

 as nearly equal as G. locusta, yet is bracketed with G, mari- 

 nws, which lias the upper or inner ramus less than half as 

 long as the lower or outer and is therefore rightly placed in 

 the first group. As G. locusta is correctly placed in the 

 second group, it follows that, in all probability, G. pulex and 

 G. campylops have been transposed and that the latter has the 

 inner ramus very short. 



Tortunately Leach's original specimens (2) from the Isle 



