CRUSTACEA. 



PART IV. 



By Thomas Wiiiteleggb, 



Zoologist, Australian Museum. 



ISOPODA. 



Pait III. 



Ill the following pages the remaining portion of the "Thetis" 

 Isopoda is dealt with, including six members of the family 

 Arcturidte, five of which are described as new species ; these are 

 as follows : — 



Arcturus simpUcissimus. 

 ,, dentatas. 



„ alcicornis. 

 ,, nodosus. 



,, serridatus. 



The sixth species (Arcturus ocidatas, Beddard) is new to the 

 fauna of New South Wales, as the types were olitained by H.M. 

 Ship " Challenii;er," oft the entrance to Port Phillip, Victoria, at 

 a depth of 33 fathoms. 



The collection includes many other interesting members of the 

 Suborder Isopoda, but these are unfortunately too imperfect to 

 allow of description. In working out the material I have been 

 seriously impeded by the paucity, imperfection, and extreme 

 brittleness of the specimens ; the latter feature I attribute to the 

 action of the formaline used in their preservation, which appears 

 to have affected the calcareous skeleton and rendered those parts 

 brittle, whilst on the other hand the connecting tissues of the 

 joints were hardened to such an extent that proper seriate 

 dissection was extremel}'- difficult. 



While preparing this paper I have had occasion to overhaul 

 the bottles containing the remainder of the " Thetis " Crustacea. 

 I found that all the examples which had been left in the original 

 formaline solution had seriously deteriorated ; as far as their 

 hard calcareous parts were concerned, they were rendered soft 

 and like newly moulted crabs. Specimens that were I'emoved 

 from formaline to spirits, immediately after being preserved, were 

 found in 2;ood condition. 



