| OCR Text |
Show 446 MR. W. E. COLLTNGE ON EUROPEAN SLUGS. [May 4, certainly not sufficient to constitute either a new genus or subgenus. In 1870 Mabille (16) gave the Arion fasciatus group, mentioned on p. 447 in this article, the name of Carinella, under the impression that all the species w'ere keeled, which, however, is not the case, as I have elsewdiere pointed out (6). Seibert in 1873 (Nachr. malak. Gesell. vol. v. p. 81) proposed the name Kolbeltia for the A. hortensls group. Later Simroth (22), 1885, divided the genus into two sections, the Monatrllclce and Dlatrlidce. In the former division all species possessing a single vestibule were grouped, and in the latter all those in wdiich the oviduct before opening into the lower vestibule dilates, thus forming as it were a second vestibule. Pollonera (19), 1887, ha3 very clearly shown that such a character as the presence of either one or two vestibules cannot serve as a basis for classification, it not being a feature of sufficient importance. Further, he thinks that Simroth attached too much importance to such a character, through his having limited his study to the few Germanic forms. Pollonera showed that we not only find in the same groups species which are Monatrllclce and species which are Dlatrlidce, but also that in the four groups into which he has divided A. hortensls two species are Diatriidce (A. hortensls and A. celticus) and two are Monatriidce (A. alpinus and A. nilssoni); further the A. bavayi belongs to the so-called Monatrllclce, while A. rufus and A. ater are the two species in which tbe Dlatrlidce condition is most marked. In a later paper (21) this distinguished malacologist points out that tbe A. hortensls from the North of France are all Monatrllclce, whereas those from Germany are Dlatrlidce, while those from the East of France are Intermediate between the two. From these facts I think it will be evident that we can no longer separate the members of the genus Arion by the number of vestibules they possess into subgenera, groups, &c. The character is interesting and may possibly be of service in separating species, but as a feature for generic distinctions is useless. Pollonera has suggested (19) the division of the genus into four groups, viz.:- 1. The Arion emplrlcorum group. 2. The Arion subfuscus group. 3. The Arion hortensls group. 4. The Arion bourguignatl group. I think this suggestion preferable to any yet proposed, and it is the one I have here followed, with some slight alterations, as shown in the following synopsis of the genus. SVNOPSIS OF THE GENUS ABION. 1. T H E Arion ater GROUP L The animal is large and unicolour in the adult. Rarely banded 1 I use the name ater for this group, as it is an older species than A. empiri-comm. |
