500 RKV. T, R. R. sTEBinxG OX CRUST ACEAXS [May 22, 



of the figures given by Mil ae-Ed wards this lobe does not reach 

 beyond thetelson, and though described as very large is represented 

 as (Comparatively long and narrow. 



Unless tlie type specimen of C. typa could be recovered and 

 examined, it would be impossible without rashness to ignore the 

 distinctions which Guerin-Meneville has drawn between it and 

 C. emargiiuUa. But tlif-y are not quite so formidable as at first 

 sight they appear. It is not very easy to induce specimens of 

 G. emarginata to lie flat, and when not flattened they have that 

 much inflated (" tres-bombe ") appearance which Milne-Edwards 

 describes. Their eyes are in fact very wide apart, and though th':^ 

 breadth of the head in comparison with the length will not answer 

 Milne-Ed wards's figure or description, in his figure there is fore- 

 shortening to be considered, and in his description we cannot be 

 sure between what points he measured the head-length. He gives 

 both a dorsal and ventral view of the animal, in the latter of which 

 the last segment of the pleon has its apex protruding rather 

 sharply beyond the uropods, whereas in the former the apex is 

 more broadly rounded and enclosed by the uropods. It is obvious, 

 therefore, that no particular stress can be laid on figures so vari- 

 able relating to the same object. In regard to the extension of 

 the first antenna? beyond the peduncle of the second, it should be 

 noted that this is much less considerable in small specimens of 

 C. emarginata than in large ones. Of the remarkable bend in the 

 basal ioints of the second and third peraeopods (4th and 5th limbs 

 of the perseon), the ventral view of C. typa shows indeed no trace ; 

 but neither does Pfeffer in his careful and elaborate account of 

 C. emarginata take any notice of this peculiarity, although he 

 explains that in all the limbs of the peraeon the first and second 

 joints are more or less firmly coalesced, but, except in the first pair, 

 plainly distinguishable. The feature to which Guerin-Meneville 

 called attention is in reality not an arching of the first joint of the 

 limb, but rather a geniculate connexion between the coalesced 

 first and second joints ; a detail much less likely to attract attention 

 in a ventral view of a small specimen than in a lateral view of a 

 large one. Against identifying C. typa with C emarginata there 

 still, however, remains a stumbling-block in the shape of the 

 uropods. Of these Milne-Edwards gives a separate figure, in 

 which the inner lobe is much longer than broad, with a narrowly 

 rounded apex : whereas in G. emarginata this lobe is little broader 

 than long, and has an oblique, slightly emarginate apical border, 

 of which the inner angle does not reach the end of the pleo-telson, 

 but the rounded outer angle reaches well beyond it. It is at least 

 possible that we have here the explanation of the discrepancy in the 

 two figures of G. typa, the artist in the ventral view observing the 

 inner angle of the uropods, and the outer angle in the dorsal view. 

 It is further possible that in the separate figure he had the uropod 

 angularly placed, so that the long distal margin appeared as part 

 of the outer side. That all this argues more carelessness in the 

 figures than ought to be imputed to a \\ork so high in reputation 

 [44J 



