72 Mr. Westwood o/i Arctiirus, 



Subgenus I . Arctunis proper. 

 Char. Suhgcn. 



Corporis segmentum 4um prEecedenti tantum pauUo longius. An- 

 tennarum externarum divisio ultima multi-articulata. Pedum 2 

 anticorum divisio ultima prsecedenti longior. Pedes 6 jDostici 

 (e figura) longitudine decrescentes. Abdomen articulis 2bus 

 anticis distinctis. 



Type. Idotea Baffini. Sabine, App. Parry's Voy, Pi, I. fig. 4 — 6. 



Syn. Arcturns tuberculatus. Latr. Regne An., 2nd edit. vol. iv. 



p. 139. 



Several specimens belonging to this subgenus, and apparently to 

 distinct species, are contained in tbe collection of the Zoological 

 Society, and formed part of the collection of Arctic Anniilosa brought 

 home in Captain Lyon's voyage. Their size is much larger than 

 that of our English species, being nearly 3 inches in length; they 

 are also much more rugose. 



Two of these specimens exhibit a remarkable peculiarity relative 

 to the natural history of the genus. 



The antennae appeared, at first sight, to be covered for a consider- 

 able distance with a mass of sea- weed, of more than half an inch in 

 diameter, so that these organs are thrust out of their natural posi- 

 tion. On examining this mass more minutely, it was, however, disco- 

 vered to be composed of the young of the animal, about a quarter of 

 an inch in length, assembled in musters of 40 or 50 upon each an- 

 tenna. One of these young ones was more advanced, being more 

 than half an inch m length. 



Subgenus 2. Leacia, Johnston. 

 Char, Subgen. 



Corporis segmentum 4tum valde elongatum. Antennarum divisio 

 ultima 3-annulata. Pedum 2 anticorum divisio ultima prsece- 

 denti multo minor. Pedes 6 postici sequales. Abdomen seg- 

 mentis 2bus anticis in unum coalitis. 



Type of this subgenus Oniscus longicornis, Sow. Brit. Misc., pi. 10. 



The body is long, narrow, rugose, and cylindric, with the head 

 and terminal segments rather broader in the male, but of an equal 

 breadth throughout in the opposite sex. This hitter is more than 

 twice the size of the males ; and in both, the body is of a whitish 

 colour, with the terminal portion generally directed upwards. 



