3 



(iij Pleupuda to a great extent branchial; the 

 Uropoda valve like, infiexed, arching- over the 

 Pleopoda - - - - ;;. Wdvifcnie. 



(2) l-ropoda terminal. (i) Pleopoda exclusively 

 branchial, generally covered by a thin ojier- 

 cular plate (the modihed 1st pair) -4. Asellota. 

 fii) Pleopoda for air breathing - o. Oniseoiiha. 

 (iii) Pleopoda when present, excdusively bran- 

 chial in the adult animal and not covered by 

 an opcrcuhim - - - (i. I'j picdrida. 



L'ujia ocediilcd belongs to the tribe Oniscoidea, which 

 are characterised by being terrestrial. This tribe includes 

 all the so-called *' wood-lice." Their abdominal append- 

 ages are htted for air breathing, but in Ligia there is a 

 very near approach to branchial respiration, as moisture 

 is necessary. The body is oval in shape, and the seven 

 ])airs of thoracic appendages are similar in character. 

 Lujia ocean icii was first described in lT(j7 by Linnaeus 

 as Oniscus ocean iciis. Later, in 1798, the genus Ligia 

 was created by Fabricius to include the Oniscus oceanicus 

 of Linnaeus. 



Biology. 



Li(/ia oceanica (PI. I.) has a wide distribution, and is 

 recorded from the coasts of the British Isles, Faroe Islands, 

 Norway, Denmark, Germany, Belgium, France, Spain, 

 Morocco and America. At Plymouth* I have found 

 Ligia most numerous, and of the maximum size, on 

 Drake's Island. At Port Erin they occur in the clift' near 

 the old biological station. 



* I wish to express my thanks to the Council of the Marine 

 Biological Association of Great Britain for the use of a table at the 

 Plymouth Laboratory, during the Easter vacation, 1906. Other 

 material for this memoir was obtained at the IMarino Biological 

 Station, Port Erin, during the Easter vacations, 1903-4. 



