540 MR, I. c. THOMPSON ON THE [June 21 , 



poph3'se aux vertebres dorsales ni de fossettes apicales ; cependant 

 le crane de G. tecpanecus, dont j'ai figure la seule partie que je 

 possedais, ressemble plus a celui diAtfactus qa'a celui de Geophis. 

 D'un autre cote les Geophis manquent de fossettes apicales at 

 d'hypapophyses, quoique ils se rapproclient par leur ensemble du 

 serpent en question ; de plus ils out les dernieres labiales supe- 

 rieures en contact avec les parictales, ce qui n'est pas le cas ici. 



II est done enddent que G. tecpanecus n'est ni un Geophis ni un 

 Atractus; mais comme il me parait avoir des affinites avec les deux, 

 je propose pour ltd un genre nouveau, celui de Geatractus. 



J'ai consulte a ce sujet une autorite en herpetologie, mon ami 

 Mr. Boulenger, qui pense que ce genre est acceptable, et que c'est 

 meme an type fort intoressant, si peu de " Calamariens " etant 

 pourvus de fossettes apicales. 



4. Contributions to our Knowledge o£ the Plankton of the 

 Faeroe Channel. — No. IV. ' Report on the Copepoda 

 collected by Dr. G. H. Fowler from H.M.S. 'Research' 

 in the Faeroe Channel in 1896 and 1897. By Isaac 

 C.Thompson, F.L.S. (With an Appendix by Dr. Fowler.) 



[Eeeeived June 18, 1898.] 



The material upon which this Report is based was collected in 

 84 out of the 41 hauls (omittiug 12/, the depth of which was not 

 recorded). The Plankton had been immediately preserved in 

 formahu, corrosive sublimate, or picric acid, and kept in 57o formalin 

 The Copepoda wei-e picked out from the mass by Dr. Fowler, and 

 sent to me in bottles labelled with the number of the station and 

 letter of the haul whence the material was obtained. 



By means of messengers iu 1897 and of a screw-propeller in 

 1896 (see pp. 570-575), the mid-water tow-nets were opened and 

 closed at will, enabling the depths to be almost accurately ascer- 

 tained, the limit of error being dependent upon the possibly impeded 

 rate of fall of the messenger or upon the accelerated rate of the 

 screw-propeller in a very heavy sea. 



The accompanying distribution table records the soundings, the 

 depths at which the various hauls were taken, the temperature (Fah- 

 renheit) at those depths, the number of meshes per inch of the net 

 used, and the occurrences of each species. It will be seen that all 

 the Copepoda collected are free swimmers, with one remarkable 

 exception, that of Argidus.xeievveA to later on. 



Tlie collection furnishes some interesting facts as to the influence 

 of depth upon distribution. By far the commonest Copepod in the 

 collection, and probably the most widely distributed species known, 

 CalaniisJinmarcMcus, occurs abundantly in 32 out of the 34 hauls, 



» For Part I. see P. Z. S. 1896, p. 991 ; Pnrt TT., P. Z. S. 1897, p. 523 • 

 Purt III., P.Z. S. 1897, p. 803. 



