1897.J MB. W. B. COLT.INGE OW EUEOPEATT SI.TTGS. 445 



Hah. Co. Dublin, Ireland ; Berkshire, Lancashire, Oxford, and 

 Middlesex, England. 



Anatomy of the Generative Organs. — The organs are generally 

 larger than those in A. hortensis, Per. There are two vestibules, 

 the lower one being considerably larger than the upper. The 

 lower portion of the sperm-duct forms a globose swelling, above 

 this a wide tube gradually tapering as it approaches the vas 

 deferens, which is sharply marked off from the sperm-duct. The 

 vas deferens is rather longer than in A. hortensis. The free-oviduct 

 is very distinct from that in any form of A. Jiortensis which I have 

 seen, and quite unlike any species of the A. Jiortensis group, in 

 having the lower portion of the free-oviduct much larger and more 

 globose than the upper, which is a narrow tube (PL XXXI. fig. 19). 

 The retractor muscle is attached to the upper part of the lower 

 division of the free-oviduct. The receptacular duct is short, ex- 

 panding terminally into the spherical sac, the receptaculum seminis. 

 The remaining parts of the generative organs are similar to those 

 of A. hortensis, Per. 



A comparison of figures 18 and 19 with those numbered 6 to 12 

 will illustrate the more striking differences. 



In fig. 6 we have the terminal ducts of the generative oi-gans 

 of a typical A. hortensis, and a variation (fig. 12) which is the 

 nearest to A. ccenileus. 



Alcoholic specimens of A. hortensis. Per., and A. cceruleus are 

 very readily distinguished from one another, even more so than when 

 alive, although the external features of A. cceruleus are much more 

 distinctly marked than in any other member of this group. 



6. Synopsis and Classification of the Oenus. 



The genus Arion as now understood by malacologists was con- 

 stituted by Perussac (11) in 1819. Brard (1815) divided Linne's 

 genus Limax into two genera, retaining Linne's name for those 

 species without a shell, and constituted the new genus Limacella 

 for those species possessing a shell. 



Jousseaume (13) is the only malacologist I know of who has 

 adopted this classification. Hartman (1821) used the name of 

 Limacia for the genus. 



Moquin-Tandon in 1855 (17) divided the genus into the two 

 following subgenera: — 



Lochea, where the shell-plate was absent and represented only by 



small, unequal, isolated granulations. 

 Prolepis, where the shell-plate was present in the form of an 



aggregation of separate calcareous particles. 



In 1868 Mabille (15) constituted the genus Baudonia for two 

 species of Portuguese slugs, B. timida and B. montana, which were 

 distinguished from Arion by being anteriorly enlarged and 

 depressed, with an almost smooth mantle, the head well separated 

 from the body, and the tentacles small. It is hardly necessary to 

 say that such superficial differences are of very little value, and 



Peoc. Zooi. Soc— 1897, No. XXX. 30 



