/ 



468 



Memoirs of the Indian Museum. 



[Voi,. V, 



the fifth ; both bear a few short setules; the flagellum is long and slender, contain- 

 ing about 30 joints and being rather longer than the peduncle. 1 



The second antenna in the male appears to be quite as slender as in the female, 

 instead of being stouter, as in Ligia oceanica. 



Ligia exotica, Roux. 



Fig. 13. — Seventh leg of male. 

 Fig. 14.— First leg of female. 



Mouth-parts. The upper lip (fig. 3, p. 463) is large and broad, covering in the 

 anterior portion of the mouth and in the living animal projecting downwards and 



1 After this was in type I received Dr. H. J. Hansen's report on the Ingolf Isopoda ("The Danish 

 Ingolf Expedition, Vol. Ill, 5. Crustacea Malacostraca. Ill"), in which he states (p. 201) that the 

 peduncle of the antenna of Ligia oceanica is 6-jointed, though it has usually been described as 5-jointed. 

 He says : 



"When the head is inspected from above and somewhat from in front, and the antenna is bent 

 downwards and turned in various directions, we find (fig. 10a) a transverse, movable piece of hard 

 chitine (1) between the head and the major outer part of next joint (2) ; that transverse piece is the 

 easily seen rudiment of first joint, and the remainder of the peduncle contains five joints. Further- 

 more a squama {ex) is observed on the outer side of third joint ; this squama is somewhat broader than 

 long, with its distal half subtriangular and freely protruding, while the proximal half has a semicircular 

 outline and is anchylosed to the joint; it may be added that this suture between exopod and joint is 

 very distinct, but in a very large specimen its median part is obscure." 



In consequence of these statements I have re-examined the antennae of L. exotica, Roux and also 

 of L. oceanica, Linné. I find little real difference between the two species in the points mentioned. In 

 both there is the small movable piece of chitin between the head and the segment of the antenna which 

 is usually looked upon as the first joint ; this is very small and I am doubtful if the evidence that it is 

 to be looked upon as a joint homologous to the succeeding one is convincing ; neither do I feel sure 

 about the squama on the third joint ; the outer margin of this joint is slightly produced in the distal 

 half in L. exotica, about as much as in L. oceanica, but as far as I can make out this portion is anchy- 

 losed to the rest of the segment, and I have previously looked upon it as a small projection forming 

 a notch or groove into which the fourth joint is received when bent back upon the third, as described in 

 the text above for the second joint. 



