MItAX GAGATES. 



143 



Fig. 165. — Median, lateral, and 

 marginal teeth of M. finustoni 

 (highly magnified), after Binney. 



Fig. 166.~Sexual organs of M. 

 hewstoni (after Binney). 



The effect of insular conditions upon the coloration of this species is 

 well parked; the broad effect being a general similarity which has a marked 

 relationship to the two prevalent varieties characterizing the British Isles. 



In Madeira this species is of a more or less dark-brown colour, and has 

 been described as var. maderensis Ckll. ; it may be regarded as an extreme 

 form of the var. rava. 



The M. gagates of St. Helena, described as forma helence, partake of the 

 characters of the vars. plumbea and rava, and the same intermediate fea- 

 tures are displayed by the forma tristensis Ckll., from Tristan d'Acunha 

 and Juan Fernandez. 



The Bermuda specimens on the contrary display a close relationship 

 with the typical form, but show a flexuous keel, and are rather more 

 opaque and rugose than is usual. 



The American examples of M. gagates, perhaps better known under 

 Cooper's name of M. hewstoni, differ but little from typical gagates ; the 

 body is blackish above, paler at the sides ; sole dull greyish ochreous ; keel 

 not conspicuous in the living 

 slug, but much stronger when 

 contracted in alcohol. The 



internal structure agrees also /^^^^ lWi^\ 



with gagates in all essential ' '^^ ^ ^^' 



points, the oviduct being said 

 by Binney to be long and very 

 I tortuous, with a well-developed 

 sperm-duct ; the vagina very 

 short, the large and globular 

 spermatheca entering about the 

 middle by a very short duct ; penis sac small, short, and cylindrical, but 

 expanded and bulbiDus at the apex, where the vas deferens enters. 



The lingual membrane has a formula of 30 -I- 1 -I- 30, with fourteen perfect 

 laterals, and shows symmetrical basal plates, and well-developed endoconic 

 cutting points to inner lateral teeth, but the marginals are not bifurcated. 



Var. bedriagae Less. & Poll., Monog. Limac. Ital., 1882, p. 59. 



Amalja mediterranea Ckll., Ann. and Mag. N.H., 1891, p. 331. 

 J^tjialia tttediterranea f. similis Ckll., op. cit., p. 332. 

 Aumlia gagates f. attantica. Ckll., op. cit., p. 330. 



Animal black, lateral areas of the sole blackish. 



The sub-var. meditePPanea Ckll. only differs from the var. bedriagce in its 

 larger size, measuring 56 mill, in length (in alcohol). It is described as of a rather 

 dull black, and though somewhat shiny, quite opaque. 



The sub-var. similis Ckll. is smaller than the preceding, has an opaque-wrinkly- 

 rugose and black body, a strong and rather flexuous keel ; side-areas of sole greyish. 



The sub-var. atlantica Ckll. is of ordinaiy dimensions, and also black, slightly 

 transparent at the sides, body smooth, with rugae not well marked ; sole grey and 

 slightly trausbicent ; jaw dark brown with a well-formed median projection. 



France — Var. bedriaga;, Nice, in the Alpes Maritimes, Signor Bedriaga (Less. & 

 Poll., op. cit.). 



Sardinia — Var. bedriagce, Signor Falchi (Less. & Poll., op. cit.). 



Sicily — Sub-var. similis, Catania (T. D. A. Cockerell, op. cit., p. .S,32). 



Spain — Sub-var. atlantica, Gibraltar, J. H. Ponsonby (T. D. A. Cockerell, op. 

 cit., p. 3.31). 



Algeria — Sub-var. mediterranea, a specimen from East Algeria in the British 

 Museum, received from Dr. Heynemann (T. D. A. Cockerell, op. cit., p. 331). 



The specimens in the British Museum, collected by Dr. Anderson at Haminam 

 Meskontina, and referred to sub-sp. mediterranea by Mr. Cockerell, are perhaps 

 better placed under the sub-var. atlantica. 



Morocco — Sub-var. atlantica, Tangiers, J. H. Ponsonby (T. D. A. Cockerell, op. 

 cit., p. 330). 



