254 Prof. J. C. Scliiodte on the 



2nd scr. vol. ii. p. 402), wliicli occurs not unfrequently in the 

 Sound near Copenhagen*. Mihic-Edwards, in his great work 

 on Cinistacea, was unable to give any information about the 

 structure of the mouth ; and Kroyer's attempt to decipher it 

 Avas necessarily incomplete, on account of the great difBculties 

 of the investigation, coupled Avith the circumstance that he had 

 only two specimens at his disposal. He treats only of the 

 mandibles and the maxillipeds ; but his statements are upon 

 the whole coiTCCt as far as they go and from his point of 

 view. He has observed the serrulate lobe of the mandible, 

 although of course he does not recognize it as an inner lobe. 

 His statement that the " maxillary lobe " of the maxillipeds 

 reaches to the apex of the palpus must be explained as 

 founded on a confused appearance of the parts caused by 

 pressure ; but it shows at the same time how far he must 

 have been from guessing that he had a mouth constructed for 

 suction before him. 



An entirely diflerent standpoint is occupied by Messrs. 

 Spence Bate and Westwood in their work on the British 

 Sessile-eyed Crustacea, inasmuch as they unhesitatingly 

 declare that the mouth in these Crustaceans " is evidently 

 formed for suction." But their account of its structure is too 

 short, and conceived in too general terms, to afford materials 

 for solving the problem now before us — viz. to understand 

 thoroughly the special construction and mode of action of each 

 part of the mouth by itself, as well as the connexions and the 



* It is still doiiljtful whether this really is a different species either 

 from A. f/racilis, Mont., or from A. gracilis, ]\liIne-Edwards. According 

 to the description o-iven by Messrs. Spence Bate and Westwood (' His- 

 tt)ry of British Sessile-eyed Cru.stacea/ ii. p. lUO) of the original speci- 

 men in the British Museum, the only one which they have seen, this 

 would differ from our species by a more slender form, the last tail-seg- 

 ment also having parallel sides, and its posterior margin being truncate 

 and in'egularly crenulated, like that of the branches of the limbs. But 

 these differences are precisely such as might be owing to the fact of 

 the specimen in question being a dried one. As for the A. gracilis 

 of Milne-Edwards, his description and figure of the tail (Hist, des 

 Ci-ust. iii. p. 13G, pi. 31. fig. 35) agree very well with our species. 

 I observe that Messrs. Spence Bate and Westwood quote A. gracilis, 

 Milne-Edwards, twice : — first (p. 100), as s}Tionymous with A. gracilis, 

 Mont., and again (pp. l(Jo and 1G7) where they refer it to their Paran- 

 thura Costnna — a circumstance which seems to require an explanation, 

 particularly because the latter animal has, according to these authors, a 

 long tail with free segments, whilst Milne-Edwards describes and figures 

 the tail of his A. gracilis as consisting of only two pieces, namely, besides 

 the terminal segment, only one other, formed by the coalescence of several 

 very short ones. In order to secure as far as possible the recognition of 

 the species examined above, I have added figures of the tail as seen from 

 the side, from above, and below, to those reprcsentinj)- the head and tlio 

 parts of tlie mouth. 



