ON THE ISOPOD GENUS LIGIA. 683 



35. A Revision of the Isopod Genus Lig'ia (Fabricius). By 

 Hakold Gordon Jackson, M.Sc, F.Z.S. ; Reader in 

 Zoology in the University of London, at Birkbeck 

 College. 



[Received May 11, 1922 : Read June 13, 1922.] 



(Plates I. & II.*) 



Contents. 



Page 



(1) Preface 683 



(2) Introduction 684 



(3) Sexual Characters 684 



(4) Generic and Specific Characters , 685 



(5) The genus GeoZi^/a 687 



(6) Key to the genus X;'^i« 689 



(7) The genus ii^ia 690 



\, Ligia ooeanica 691 



2. I/igia pallasii 691 



S. Liffia glahrata 692 



4. Ligia occidentalis 692 



5. Ligia cinerascens 698 



6. Ligia exotica 693 



7. Ligia olfersii 694 



H. Ligia italica 695 



9. Ligia gracilipes 695 



10. Ligia hawaiensis 696 



W. Ligia nov(B-zealandice 697 



12. Ligia haudiniana 698 



13. Ligia 'pigmentata 699 



U. Ligia joerJcinsi 699 



15. Ligia natalensis 700 



Species described by other authors 701 



Doubtful or insufficiently described species 701 



Bibliography 702 



Explanation of the Plates 703 



(1) Preface, 



This paper on the genus Ligia is intended to be the first of a 

 series dealing with the Terrestrial Isopods. The opportunity of 

 undertaking the work was given to me by Dr. W. T. Caiman, 

 F.R.S., who placed at my disposal the material, now in the 

 possession of the British Museum, which belonged to the late 

 G. Budde-Lund. The author of ' Isopoda Terrestria ' evidently 

 intended to use this material, which comprises specimens of most 

 known species of terrestrial Isopods, for the revision of his great 

 work on which he was engaged at the time of his death. He was 

 only able to complete the genera Euhelum, Armadillo, and the sub- 

 family Spherilloninse, but he left notes of observations on other 

 genera which will be referred to in their proper place. I propose 



* For explanation of the Plates see p. 703. 



