147 



ON THE ANATOMY AND SYNONYMY OF THE GENUS 



MARI^LLA, Gray. 



By Wilfred Maek Webb, F.L.S., etc., 

 ; Assistant Lecturer on Biology to the Essex County Council. 



Bead 10th June, 1898. 



PLATE IX. 



Some time ago our member, Mr. Oliver CoUett, F.E.M.S., sent 

 a number of slugs from Ceylon to the writer for description. One 

 species amongst these, however, can be identified as having been 

 described before upon more than one occasion, while it, or a nearly 

 allied form, has, three or four times over, had a new genus specially 

 created for its reception. 



A rough anatomical investigation of one of the specimens under 

 consideration revealed its relationship to the members of the genus 

 Girasia, Gray, the structure of which has been investigated by Lieut.- 

 Col. Godwin- Austen ^ ; and a reference to a manuscript list of Cingalese 

 slugs kindly furnished by Mr. E. R. Sykes showed the occurrence of 

 Tennentia Thivaitesii, Humbert, and Vega Nordenskiolcli, Westerlund, 

 in the island. These two last forms, with Dehhania Beddomei, 

 Godwin-Austen, from the south-west of India, are put by Cockerell, 

 in his "Check-List of Slugs,"* into the genus Marmlla, Gray, the 

 type species of which is Marmlla jDiissumieri (Valenciennes MS.), 

 Gray, from Mahi. In a note^ Cockerell gives his impression that 

 all the forms alluded to belong to the same species, and he must also 

 be credited with having previously* placed them in Gray's genus, but 

 without giving the reasons in detail. 



The material belonging to the British Museum (Natural History), 

 which was examined through the courtesy of Mr. Edgar Smith, consists 

 of Gray's type-specimen of M. Dussiimieri and two examples from Ceylon 

 labelled Tennentia Thwaitesii, Humbert, by Cockerell. There is no 

 record of the last two slugs, though it is probable from the date upon 

 the bottle (and from the fact that the Museum acquired other 

 specimens procured by Thwaites) that they were collected by the 

 man whose name they bear and are really the fellows of those 

 described by Humbert. 



^ Proc. Zool. Soc, 1880, pp. 289-299; Land aud Fresh-water Mollusca of India, 



p. 2'20, pis. xxiv-xxvi. 

 2 Conchologist, vol. ii (1893), p. 186. 

 •' Tom. cit., p. 204. 

 * Ann. & Mag. Nat. Hist, ser. vi, vol. vii (1891), pp. 103 & 104. 



