GEOMALACUS. 243 



been given to a young Arion, the number of the species could 

 be most readily increased. 



The substitution has doubtless been no easy task for Mabille 

 in the composition of his monograph ; but he must have formed 

 for himself a totally different conception of the animal, which 

 had hitherto been described by English authors only, though 

 with sufficient distinctness. In his generic diagnosis, Mabille 

 states that the animal is ornamented with an infinite number 

 (" d'une infinite ") of minute black, yellow, golden, white or 

 silvery dots, which, by the by, is by no means correct ; and in 

 his improved specific diagnosis he even amends the original 

 English descriptions in so cool a manner that I am astonished 

 that English malacologists should not have replied to it. Mabille 

 says in the same diagnosis, that the English draftsmen, instead 

 of covering the body of this slug with a multitude of white 

 dots, had contracted the same upon the wrinkles, and to facili- 

 tate their labor, had united them into one single spot on the 

 different wrinkles. And this, he states to be the reason why the 

 Geomalacus appears to be a black animal with longitudinal 

 white ridges or hillocks, and which, he says, is quite incorrect. 

 This statement of itself suffices to convince us that Mabille has 

 never seen a living Geomalacus ; for what he supposes to be 

 altogether incorrect is precisely the actual fact. The Geomalacus 

 is not covered with white or yellow dots, but with actual longi- 

 tudinal spots extending on the back of the animal over one or 

 two of the wrinkles. These spots are even distributed on a 

 black ground in such a manner that they might easily be 

 counted ; and the drawings of Allman are quite correct. 



Mabille 's description of the respiratory orifice as being con- 

 siderably in front (" tres anterieur"), corresponds admirably 

 with that of a young Arion. The original diagnosis says, " a 

 Limace (differt) situ anteriori spiraculi ; " for in the Limax the 

 respiratory orifice is situated behind the middle of the mantle, 

 and not in front of it. Further incorrect is Mabille's statement 

 respecting the internal shell namely " Limacelle delicate, ex- 

 cessivement plate ; " and, further, " Sa Limacelle mince comme 

 une pellicule." The original diagnosis says u Testa solida ; " 

 and, indeed, its thickness attains almost a third of its length, and 

 nearly the half of its breadth. The shell is consequently by no 



