tn the Amphipoda. 371 



thus the relative lengths of the various joints of the antennge 

 are subject to slight variations ; in large specimens the lower 

 antennae increase in length as compared with the upper, and 

 the flagellum of the upper antenna decreases in length as 

 compared with the peduncle. 



The stout curved setse on the end of the flagellum of the 

 lower antenna in Microdeuteropus teniiipeSy mentioned bj Mr. 

 Haswell, are present in the other forms ; but in many of the 

 specimens they are not very prominent, and they have conse- 

 quently not been mentioned by other observers. 



Mr. Thomson described the appendage to the mandible of 

 Microdeuteropus maculatus as i^^f-jointed. In M. Mortoniy 

 M. tenuipes^ in the Lyttelton specimens of M. maculatus^ both 

 male and female, and of Aora typica^ it is (fAree-jointed, as is 

 almost universally the case with the Amphipoda, and in the 

 Dunedin specimens of M. maculatus and Aora typica which 

 I dissected I found it also three-jointed ; the first and second 

 joints lie nearly in the same straight line, and though the 

 division between them is distinct enough, they do not appear 

 to be very movable one upon the other; and I fancy this has 

 given rise to the error in Mr. Thomson's description, which is 

 in all other respects exceedingly accurate. In this species, as 

 in many others of the Amphipoda, the cutting-edge of the 

 mandible is not quite the same on the right side as on the 

 left, but the differences in this case are small. On the distal 

 portion of the third joint of the appendage are two rows 

 of long serrated hairs, of which those at the end are the 

 longest and are most closely approximated to one another, 

 and between these are two rows of short straight setse. It is 

 not very easy to get a good view of these rows in the proper 

 position ; when seen in side view they present the appearance 

 of a dense fringe on one side of the joint, as shown in Mr, 

 Thomson's figure*. In his description of Aora typica 

 Mr. Thomson says, '^ telson quite smooth." In all the speci- 

 mens that I have examined the telson is essentially the same as 

 in Microdeuteropus maculatus, viz. the projecting portion on 

 each side is slightly notched at the end and bears one or two 

 slender spinules. 



It is curious to note the variations in the parts in which the 

 males and females of different species of the Amphipoda re- 

 semble and differ from one another. Thus in some species 

 of Mcera, such as M. siihcarinata, M. festiva, and in Melita 

 tenuicornis, Podocerus jreqitens, Podocerus longimanus, Para- 

 noinia typica, Nicea egregia, &c., the male differs from the 

 female in the structure of the second pair of gnathopoda, while 

 * Aun. & Mag. Nat. Hist. ser. o, vol. iv. pi. xvi. fig. 7. 



