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XXIII.— A Revision of the British Idoteidge, a Family of Marine Isopoda. By 

 Walter E. Coffinge, D.Sc, F.L.S., etc., Research Fellow of the University of 

 St Andrews. Communicated by Professor M'Intosh. (With Eleven Plates.*) 



(MS. received December 11, 1915. Read January 10, 1916. Issued separately January 17, 1917.) 



CONTENTS. 



I. Introduction . 



Methods and Technique 



II. Historical 



III. Classification and Affinities 



IV. Geographical Distribution 



V. Variation 



VI. External Structure — 

 (a) General Form 

 (6) The Cephalon 



1. The Eyes . 



2. Antennulae . 



3. Antennae 



4. Oral Apj>endages 



(c) The Mesosome 



1. Coxal Plates 



2. Appendages . 



(d) The Metasome . 



1. Appendages . 



2. Uropoda 



VII. Bionomics and Economics 



PAQK 

 721 



722 

 723 

 724 



727 

 728 



730 



730 

 730 

 .730 

 731 

 731 

 732 

 732 

 732 

 732 

 733 

 733 



733 



PAGK 



VIII. Systematic . 734 



Family Idoteid;e, Leach, 1813 



Key to the Genera of British Idoteidae 



1. The Genus Idotea, Fabricius, 1798 

 Key to the British Species 



(1) Idotea baltica (Pallas) 



(2) „ pelagica, Leach 



(3) „ neglecta, G. O. Sars 



(4) „ emarginata (Fabr.) 



(5) „ granulosa, Rathke 



(6) ,, sarsi, n. sp. 



(7) „ viridis (Slabber) 



(8) „ metallica, Bosc 



(9) „ linearis (Pennant) 



2. The Genus Zenobiana, Stebbing, 1895 



(1) Zenobiana prismatica (Risso) 



3. The Genus Synisoma, nov. nom 



(1) Synisoma lancifer (Leach, MSS.) 



(2) „ acuminata (Leach) 

 Bibliography . . ... 

 Explanation of 1 Mates 



735 



736 

 736 

 737 

 737 

 739 

 740 

 741 

 742 

 743 

 745 

 746 

 747 

 749 

 749 

 750 

 751 

 752 

 753 

 756 



Index 759 



I. Introduction. 



Many of the earlier accounts of the group of Crustacea, known as Isopoda, suffer 

 from want of more detailed diagnoses and figures. To some extent this has been 

 remedied during recent years by the authors of different monographs, but there are 

 still many families which remain somewhat obscure, or only partially understood, 

 owing to the above-mentioned cause. Such a family is the Idoteidae. 



In the present communication I propose to revise the diagnoses of the British 

 genera and species, to set forth in greater detail than has hitherto been done their 

 structure, illustrating the same, and to discuss the classification and affinities of the 

 family as a whole. 



This investigation has been carried out at the Gatty Marine Laboratory of 



St Andrews University, during my tenure of a Research Fellowship of the 



University, and of a Walker Trust Research Scholarship. 



* The author desires to thank the Carnegie Trust for the Universities of Scotland for their grant to meet the 

 cost of reproduction of the plates. 



TRANS. ROY. SOC. EDIN., VOL. LI, PART III (NO. 23). 106 



