198 PROFESSOR CHARLES CHILTON ON THE 



of Metopa sarsii Pfeffer. This specimen I have been allowed to dissect and mount 

 permanently as a micro-slide, and I find it agrees precisely with M. ivalkeri Chevreux, 

 a name which must therefore be dropped in favour of the older M. sarsii. 



My specimens agree minutely with CHEVREUX'S description ; the accessory 

 flagellum is, I think, present in all the specimens, but it is exceedingly small, so small 

 that it would hardly be inaccurate to say that it is absent. CHEVREUX describes the 

 palp of the mandible as two-jointed ; I think there is a minute third joint present in 

 the specimen from which I dissected the mouth parts, but if so it is almost as small as 

 the accessory flagellum ; yet the presence or absence of these minute joints is one of 

 the distinguishing marks for some of the genera into which the family Metopidae is 

 now divided. 



CHEVREUX was unable to identify his species with any of those described by 

 STERBING in the Challenger Report, but says it seems to be nearest to Metopa ovata ; but 

 this species has the basal joints of perseopods four and five narrow, and is now placed 

 in the genus Metopella. I would rather be inclined to compare it to M. magellanica 

 or M. compacta, species now placed in the genus Metopoides, while the small acute 

 teeth which are present on the palm of the second gnathopod, as described by 

 CHEVREUX, show an approach to the more irregular palm found in M. crenatipalma, a 

 species now known as Proboloides crenatipalma. 



From the Challenger collections STEBBING described six species of Metopa one 

 from Kerguelen Island, the other five from Cape Virgins, off Patagonia ; each of which, 

 with one exception, was represented by one specimen only, though of one species 

 another specimen was found at Nightingale Island in the Tristan da Cunha group. Of 

 these six species three are placed in Das Tierreich Amphipoda under Metopoides, two 

 under Metopella, and the other under Proboloides. As these genera are separated 

 from one another and from Metopa by small points such as those I have mentioned 

 above, and as there are altogether twenty-one species of Metopa, six of Metopella, 

 three of Metopoides, and seven of Proboloides, it is not to be wondered at that the 

 classification of the family is admittedly in an unsatisfactory condition, and I think it 

 wisest not to attempt to identify the species under consideration with any of the 

 Challenger species, although it is probably the same as one of the species described 

 from Cape Virgins. 



The sides of the last segment of the urus are raised into a vertical plate on each 

 side of the telson, and this is continued by a similar vertical plate on the outer edge 

 of the peduncle of the third uropod, so that a groove is formed, protected on each side 

 by these vertical plates or flanges, in which the telson may rest when the animal swims 

 by backward strokes of the hinder part of the body (see Plate I. fig. 10). 



(ROY. soc. BDIN. TRANS., VOL. xt.vin., 480.) 



