I 3 S 



CRUSTACEA PERACARIDA 



CHAP. 



tion. <:>ne .species. /'. /m(<?at<:i, being entirely marine, in the 

 Arctic and North Atlantic, P. ajfinis inhabiting the Atlantic, 

 and also freslnvater lakes in Europe and Xorth America. 

 P. microphthalma being confined to the Caspian Sea, and P. loyi 

 to Lakes Superior and Michigan. 



Fam. Gammaridae. Includes fifty-two genera. The first 

 antennae are slender, with the accessory flagellum very variable. 

 The mandibles have a dentate cutting edge, spine-row, and molar 

 surface, and a three-jointed palp. The first two thoracic limbs 

 are subchela:- This family includes a few marine, but mostly 



Abd.l 



FIG. 9">. Gammfirn-s and ? (below, x 4. Abd.l. First abdominal 



_ tent : T. teNon : 77*, seventh free thoracic segment ' = 8th thoracic segment : 

 U, third uropod. 'After Delia Valle.) 



brackish and freshwater species. ("'/">?//<'////./ is entirely subter- 

 ranean in habitat, as is Xipliarg-ns. X. f<rr(Ui occurring, however. 

 in the deep waters of Lake Geneva. Both these genera are blind. 

 "i/tc/'t/s has thirty >pei/ie.s, (/. 7oi-i/*tn being the common species 

 on the Xorth Atlantic coasts, and O. pvlex the common freshwater 

 species <>f streams and lakes in Europe. A number of Gammaridae 

 inhabit the Caspian Sea, e.g. BoecLia, Gmelino. Niphargoides, etc., 

 while the enormous Gammarid fauna of Lake Baikal, constitut- 

 ing numerous genera, showing a great variety uf structure, some 

 of them being blind, belong to this family, e.y. MacrohectopuS 

 (Constantia), Acanthogammarus, Heterogammarus, etc. 



