794 



THE POPULAR SCIENCE MONTHLY. 



It will probably not be welcome news to some of our readers that 

 the English crayfish is in all probability not entitled to the current 

 title of Astacus fluviatilis. This name appears to belong to a larger 

 species, sometimes called A. nobilis, hardly distinguishable from the 



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^ ,' ((/7j8 arb') jill\2 art 13 p{(»i3 





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Fkj. 5.— Astacus flcviatilis. In A, the ^ills, exposed by the removal of the branchiostegite, 

 are seen in their natural position ; in B, the podobranchise are removed, and the anterior set 

 of arthrobranchiiE turned downward ( x 2) : 1. e>e-stalk; 2, antenrule; 3, antenna; 4, man- 

 dible; 6, scaphognathite ; T. first maxillipede, in B the epipodite, to which the line points, is 

 partly removed ; 8, second maxillipede ; 9, third maxillipede; 10, forceps; 14, fourth ambn- 

 latory leg; 15, flrst abdominal appendage ; xv„ first, and xvi., second abdominal somite ; a?'b. 

 8, arb. 9, arb. 13, the posterior arthrobranchiae of the second and third maxillipedes and of the 

 third ambulatory leg ; arb'. 9. arb'. 13, the anterior arthrobranchice of the third maxillipede and 

 of the third ambulatory leg; pbd. 8, podobranchise of the second maxillipede ; pbil. 13, that of 

 the third ambulatory leg ; plb. 12, plb. 13, the two rudimentary pleurobranchise ; plb. 14, the 

 functional pleurobranchiae ; r, rostrum. 



English one, which in France lives side by side with it. The smaller 

 crayfish, which alone occurs in England, is known as A. torrentium. 

 This specific title will, it is to be feared, have to be adopted, although 

 it by implication casts a slur upon the river Isis. A. fluviatilis hsi^ 

 red tips to its legs and a rostrum which differs by a notch or two 

 from that of A. torrentium. Further, and this is very curious, A. 

 torrentium never has been found to be infested by that very interest- 

 ing parasite (more interesting even than the crayfish itself), the crab- 



