(iAM.M AKID.K. 20') 



Unfortunately the liabitat of this crustacean is not known. The 

 species is of considerable interest, as associatinc,- the fjenera Amalliin 

 and (huHnutravdntliHXw'iiXx GdiiniKirus. 1 know of no other tlistinctly 

 carinated species that carries the dorso-caudal fasciculi of spines. 



Tliis inav he (ntnuiutrxs mHcrondftin of Say ; hut the specimens in 

 the British Museum labelled as belonginji; to this last-named species 

 do not correspond with the vciy meagre desciiption of the author, so 

 that I do not feel justified in assuming Say's name without a clearer 

 conception of the North American type. 



This species is preserved in the ^Museum of the Jardin des Plantcs, 

 it ha\'ing formed a portion of the undescribcd collection enti'usted to 

 me by Professor Milne-Edwards for description in this Catalogue. 



2. Gammarus Pulex. (Plate XXXVI. fig. 4.) 



Gammarus Pulex, Fah. But. S;/st. ii. p. ^K?. no. 7. 



Ldtrcilh; Gen. Crust et Lis. i. p. 58. 



Koc/i, I)('utsr]>l. Crust., Mi/r. u. Arachn. p. 8B. no. 21. 

 Cancer Pulex, Linn. Hi/st. Nat. iii. p. 1055. no. 81. 



Rueself Ins. iii. p. 351. t. G2. f. 1-7. 



" G. caesius, dorse fusco-testaeeus, segmentis posterioribus postice 



medio in dentem acutum productis." — Koch. 

 Length 6 to 7 lines. 



Hah. In large streams and ponds, generally found in great abun- 

 dance. 



Koch remarks that the animal is readily distinguished from Gam- 

 marus jiuinatllis* by the dorsal teeth upon the fii'st three segments 

 of the pleon. The colour throughout is of a greyish-brown mottled 

 ■with yellow, having the dorsal dental processes blotched A\'ith scarlet ; 

 there are similar spots on the sides of the animal, and also smaller 

 ones of the same colour on the coxa). 



Authors generally appear to have given the names of Pulex and 



Jtuviatilis indifferently to the common freshwater form. Koch and 



Latreillc have figured G. Pulex with dorsal teeth. I have therefore 



confined the latter name to this species, and have not quoted any 



authorities besides those Koch has given. 



3. Gammarus subcarinatus. (Plate XXXVI. fig. 5.) B.M. 

 Gammarus subcarinatus, Stimpson, 3IS', 

 First three segments of the pleon having the dorsal median Line 

 slightly elevated into a carina, and terminating posteriorly in a 

 fiusciculus of short spines ; a fasciculus of spines also exists upon 

 each side, increasing in importance posteriorly upon all the seg- 

 ments of the ])leon : the last three segments of the pleon have 

 • no central c-arina. Eyes oval. AntenniC sube(pial, one-third the 



* G. ft)ssr/ri/T)i, Koc]i. 



