MYSIDACEA 



I 19 



(Fig. 79) described by Sars, 1 may be chosen as an example of 

 the Mysidacea. 



The peculiarity of this form consists chiefly in the immense 

 elongation of the endopodites of the fifth, sixth, and seventh thoracic 

 appendages. Characteristic of the Mysidacea is the freedom of 

 the hinder thoracic segments from fusion with the carapace, other- 

 wise this animal is seen closely to resemble the Euphausia figured 

 (Fig. 102). Eucopia australis, like so many of the Mysidacea, is a 



FIG. 79. Eucopia australis, young female, x 3. A, 1st antenna ; Ab.l, 1st 

 abdominal segment ; Ab.6, 6th abdominal appendage ; E, eye ; T, telson ; Th, 5th 

 thoracic appendage. (After Sars.) 



deep-sea animal, being brought up with the dredge from over 1000 

 fathoms ; it is very widely distributed over the Atlantic Ocean. 



Fam. 2. Lophogastridae. - - The members of this family 

 (Lopkogaster, GnatJiopkausia) agree with the Eucopiidae in the 

 possession of branched gills on some of the thoracic limbs, in the 

 absence of auditory sacs on the sixth pair of pleopods, in the 

 presence of normally developed pleopods in both the male and 

 female, and in the brood-lamellae being developed on all seven 

 of the thoracic limbs. The endopodites of the posterior thoracic 

 limbs are, however, of a normal size. 



Fam. 3. Mysidae. These differ from both the foregoing 

 families in the absence of gills, in the presence of an auditory 

 sac on the sixth pleopods, in the reduction of the other pleopods 

 in the female, and in the brood-lamellae being developed only on 

 the more posterior pairs of thoracic limbs. A number of closely 

 1 Challenger Reports, vol. xiii., 1885, p. 55. 



