64 Description of Genera and Species. 



spatulated, and flexes backwards with the next joint, wliich is subquadrate in form, 

 flattened laterally, and with a strengthening keel. This joint also flexes back upon a 

 long joint, longer than the two combined. This joint is laterally compressed and has a 

 longitudinal strengthening keel. It is bent upwards and flexes forwards upon the fourth 

 observed joint, making a sort of elbow with it. This joint is short and flexes forwards 

 upon a fifth short joint of similar character seen in fig. 3. The whole construction of 

 this limb reminds one powerfully of the limbs in the family of the Perimecturidffi, 

 already described, and looks more like a raptorial limb than a gnathopod. The nature 

 of tlie exopod of this limb has not been observed. The legs consist of seven pairs, all 

 constructed much alike, but diminishing in size in backward succession as seen in fig. 1. 

 The limbs are slender and arranged so that all the proximal joints of each leg flex 

 forward ; the distal joints flex backwards at the same relative joints in each leg. The 

 tip joints are short and somewhat pointed, and flex back upon a longer joint, this in 

 turn flexing also back upon a short joint which flexes back upon a long upturned one. 

 The three combined joints are about equal in length to this long one. The long joint 

 flexes forward on a short joint, making an "elbow," and this joint in turn flexes for- 

 wards upon a second short one; but the limb can be traced no further, owing to the 

 swollen bases of the exopodite hiding what is probably the coxal joint. These limbs 

 are pitted along their margin for seta3, and there can be no doubt that they agree in 

 almost every respect with the more anterior limbs in Euphausia, but, unlike that genus, 

 all the seven pairs of limbs are alike except in size. All are supplied with exopodites, 

 the muscular basal joints of which are generally visible; but whether they ended in 

 swimming plates or lashes has not been determined. No breeding lamellaa or brood 

 pouch have been observed in the females, nor have gills with certainty been 

 recognised ; but the small round luminous organ has been observed on the last body 

 segment in several specimens (figs. 1, 2, 5). The most notable character about the 

 appendages of the tail is the enormous development of the limbs on the first two tail 

 segments in the males, which are even more massive relatively to the size of the form 

 and to the other pleopods than in the recent members of the family. The first pair are 

 especially massive (figs. 1, 4), and consist of a strong, forward-curved, basal joint, to 

 which is articulated a second joint which is either bifid or nearly so, and gives two 

 branches. The inner branch terminates in a scoop-shaped plate, from the inside of 

 which project coupling hooks. Two of these are shown projecting beyond the doubled 

 up plate in fig. 1, a further magnified part in fig. 1^. The details of the arrangement 

 of hooks have not been made out from the available material, but sufl^cient can be seen 

 to show that these ancient forms had the same habit as their recent congeners of 



