PROTOMEDEIA. 297 



A M PHI POD A . OA MM A RIDES. 



NATATOE1A. 



Genus PROTOMEDEIA. 



Protomedeia. KROYER, Tidskr. iv. p. 154. 



Leptocheirus. ZADDACH, Syn. Crust. Prussicorum Prodomus, p. 7. 



Ptilocheirus. STIMPSON, Mar. Invert, of Grand Manan, p. 55. 



Generic character. Like Microdeutopus, but having the 

 second pair of gnathopoda not subchelate. 



THIS genus is probably too closely associated with the 

 preceding. But the form of the second pair of legs 

 offers a similar ground of distinction as that which 

 separates Talitrus from Orchestia. The coxae, moreover, 

 appear to be rather deeper in this genus than in 

 Microdeutopus; and the last pair of legs are not so 

 proportionally long as compared with the sixth pair. 

 The last pair of caudal appendages are double branched. 

 We are uncertain as to the character of the central 

 caudal plate since most of the specimens we have had 

 an opportunity to examine have been more or less im- 

 perfect, but in P. Whitei it appeared to be double, whilst 

 Zaddach defines it as being sub-membranous and rounded 

 above. 



The animals of this genus, though not abundant, 

 appear to be widely distributed in the colder regions ; 

 specimens being taken on the northern coast of the 

 United States of America, on the coast of Scotland, in 

 the Baltic, and off the shores of the Crimea. 



