328 Canon A. M. Norman on 



A. Clausi. In the same year Professor G. O. Sars pub- 

 lished his work on the Mediterranean Isopoda Chelifera (103), 

 in which full illustrations were given of a Mediterranean 

 Apseudes, which he had previously characterized (101) under 

 the name A. acutifrons, G. O. Sars. Professor Claus, re- 

 plying to the criticisms of Boas on this and other points in 

 his second memoir (17), argued that the Adriatic form he 

 had described was the true Rhoea Latreillii oi Milne-Edwards, 

 and that it was the same species as A. acutifrons, G. O. Sars, 

 which latter name must become a synonym of the former, 

 ■while the A. Latreillii of Bate and Westwood, of Norman 

 and Stebbing, and of Sars must be renamed as A. Sarsii, 

 Claus. It is necessary, therefore, to carefully examine the 

 form described by Milne-Edwards. Rhoea Latreillii, H. 

 Milne-Edwards, was twice figured by its describer, originally 

 in Annates des Sci. Nat. vol. xiii. 1828, p. 292, pi. xiii. A, 

 figs. 1-8, and then again in ' Regne Animal Cuvier. Les 

 Crustace's,' par Milne-Edwards, pi. Ixii. fig. 2. A com- 

 parison of these figures brings out some important points. 

 In both figures the hand of the second gnathopod is repre- 

 sented as armed with four spines and the wrist with one : 

 in the ' Annales ' fig. 2 represents a conspicuous rostrum, 

 and the last segment of the pleon is of considerable length, 

 as long as the three preceding segments ; in the larger figure 

 which we find in the ' Begne Animal ' the rostrum has the 

 proportions of that of Spence Bate's Latreillii, and the large 

 pleon-segment only equals the length of two preceding seg- 

 ments. Taking these facts together, and the general details 

 of the figures as well as the description, it would seem that 

 M.-Edwards's species cannot be A. acutifrons, Sars. First, as 

 regards the rostrum, the description " extre'mite' ante'rieure 

 se prolonge sur la forme d'un rostre pointu et le*gerement 

 recourbe'e," applies closely to Latreillii *, but scarcely to 

 acutifrons-. the last segment of pleon is described as " re- 

 marquable par sa longueur " ; it is represented in the 'Annales' 

 as equal in length to the three preceding segments, but in 

 Cuvier as equal to only two — in the former case resembling 

 that of acutifrons, in the latter that of Latreillii. The 

 fossorial second gnathopods are both described and figured as 

 having four spines on the margin of the hand and one on 

 the carpus : now acutifrons has four on the hand and two 

 on the carpus, six in all on these two joints ; while Latreillii 

 has three spines on the hand and two on the carpus, five in all. 



* Henceforward I shall use the term " Latreillii" for Latreillii, Bate 

 and "Westwood. 



