LIMAX. 15 



them, L. brunneus and tenellus, are doubtful. The first is not im- 

 probably the young of a dark variety of L. agrestis, while the 

 second is founded on a single specimen collected many years ago, of 

 which the specific value has not been confirmed by subsequent re- 

 search. L. brunneus, though reported by M. Bouehard-Chantereaux 

 in 1838 to be breeding abundantly in the vicinity of Boulogne, is 

 included by M. Moquin-Tandon, the highest and latest authority on 

 the subject, along with L. tenellus in his list of ' Especes Incertaines.' 



There are, then, six undoubted species of Limax in the British 

 Isles, all continental types, affording good distinguishing peculiarities 

 of form, general marking, and habit. The series embrace two very 

 obvious divisions, L. Soiverbyi and gagates, constituting the sub- 

 genus Milax of Gray, Amalia, of Moquin-Tandon, have the shield 

 granulated like that of Avion; and, Hke Avion the rudimentary 

 shell which it encloses is little more than an irregular agglomerate of 

 calcareous particles. It is, however, more constant, of a more re- 

 gular ovate form, and in developing a rudimentary nucleus, presents 

 a nearer approach to shell-structure. Another pecubarity of this 

 division of the Limaces, more conspicuous in appearance, but of less 

 physiological value, is the presence of an erect keel, along the whole 

 length of the back, reaching from the shield to the extremity of the 

 tail ; while, in the species which follow, the back is keeled in a less 

 prominent manner only towards the tad. The mantle, here desig- 

 nated the shield from the peculiarity of its form and office, is that 

 part of the animal to which the conchologist will probably direct 

 his attention — the shell, of which we have so nicely graduated a 

 development in the genera of this famfiy, being no unimportant 

 part of the animal. 



In the remaining four species of the genus, L. agrestis, mavginatus, 

 flavus, and cineveus, forming the subgenus JEulimax of Moquin- 

 Tandon and Gray, the shield is striated with wrinkles which are dis- 

 posed in regular concentric order ; and the shell becomes, in its 

 fullest development in the last-named species, an oblong square valve, 

 constructed of symmetrical additions of growth around an umbonal 

 nucleus. An epidermis of thin horny tissue is also formed. 



We have said that our six undoubted species of Limax are all 

 continental types. They are the only satisfactorily estabbshed 

 species in Europe. ISTot that the continental conchologists have been 

 backward in describing species. Ko less than forty have been re- 

 corded as natives of Europe, the greater portion of them, according 

 to Dr. Grateloup, living in France. Yet M. Moquin-Tandon, in his 



