654 PATAGONIAN EXPEDITIONS : ZOOLOGY. 



rest) in the spiniform prolongation of the segments of the pleon. This 

 character, however, seems to be of minor importance, since there are 

 intergradations in this respect between the typical H. dentata and H. 

 inermis in the United States (see Smith, 1874, Fish Comm., p. 647 ; 

 specimens from Florida). Faxon regards H. inermis only as a variety 

 of H. dentata. 



In all other characters, H. dentata as well as H. inermis are closely 

 allied to our species, especially the following characters agree : 



1. General shape of body and eyes. 



2. Length of antennulae and antennae. In H. dentata and H. inermis 

 these are considerably shorter than half of the body. 



3. Shape of the second gnathopod of the ^. Especially the propodite 

 is directly identical, as will be seen by comparing our figure (3^') with the 

 figure of this joint of//, dentata (j* ad.) given by Smith (1874, Geol. Surv., 



pl. I. f. 3). 



4. Relative length of the peraeopoda. 



5. Shape of uropods and telson. 



The chief differences are the following : 



1. The number of joints of both antennulae and antennae is greater in 

 our species. Although these parts are about as long as those of //. den- 

 tata and inermis, the number of joints is slightly greater in H.patagonica 

 (in dentata and inennis, 7-9 in the antennulae, 8-12 in the antennae; in 

 H. patagonica, 8-12 in the antennulae, 9-17 in the antennae). The joints 

 of the peduncles are a little different in length ; while of those of the an- 

 tennulae, in //. dentata and inermis, the two distal ones are about alike, 

 the last joint, in our species, is a little shorter than the second. In the 

 antennae, the second and third joints are alike in //. dentata and inermis, 

 while, in //. patagonica, the third is distinctly longer than the second. 

 These differences, however, seem to be of minor importance. 



2. In the first gnathopod of the ^ as well as the $, the propodite is, in 

 H. patagonica, distinctly broader and more triangular ; the propodite has a 

 distinct lobiform prominence, which is much more developed than in H. 

 dentata and inermis, and, consequently, the carpopodite appears shorter 

 and broader in our species. 



3. The same is true of the second gnathopod of the 9 : the carpopodite 

 and propodite are shorter and comparatively broader in our species, and 

 the process of the carpopodite is more pronounced. The propodite in H. 

 dentata and inermis is much longer than in our species. 



