ANADENTJS. 469 



be attributed to the situation of the lung-orifice, as this has not 

 been observed in living specimens. In dead examples of Anadenus 

 it is indeed practically in the middle, but the anterior, free, part 

 of the mantle invariably contracts far more than the posterior 

 adherent portion, and since in dead specimens of Limax, this 

 opening is likewise in the middle while in the living state it is 

 placed further back, it is not likely to be different in Anadenus. 



" The new genus is probably nearest to Geomalacus occurring in 

 Great Britain, which hitherto I have not had an opportunity of 

 examining, but from which it may be distinguished by the 

 following characters : 



Geomalacus. Anadenus. 



Tail portion : round. pointed. 



Respiratory orifice : at the behind the middle. 



middle of the mantle. 



Caudal gland : present. absent. 



Internal shell : absent. present. 



" Although similar, not only in general form, but also as regards 

 the position of the respiratory and genital orifices, as well as in 

 the presence of an internal shell, it must not be confounded with 

 Limax, for in addition to the difference in the jaw, it is 

 distinguished by the form of the tail portion which, in Limax, is 

 invariably keeled while in Anadenus it is without any trace of 

 keel. 



" If we could only observe living specimens or obtain an accurate 

 description of them, undoubtedly further differentiating characters 

 between similar or allied forms would be found, such as the shape 

 of the rugae of the mantle and of the body. 



" As I have already observed on a former occasion, in dead 

 specimens the wave-like rings on the mantle of Limax disappear. 

 Nor can it be stated whether the mantle of Anadenus is granulated 

 as in Arion, Amalia, and Geomalacus, or whether it has the well- 

 known structure of Limax. The ruga3 on the back likewise 

 become depressed and no accurate description of them can be 

 made from spirit-specimens ; yet, it is evident from the illustration, 

 which I give of the skin of the back of a dead Anadenus, that it 

 really differs from all known forms. A furrow runs along the 

 middle of the back, from which lateral furrows, obliquely directed 

 backwards, branch off. The areas enclosed by these furrows are 

 covered with a double row of irregularly diverging ruga3." 



The only extralimital species known is A. sinensis, Mollendorff *, 

 from Se-Chuen. 



Ann. Mus. Zool. Acad. Imp. Sci. St. Petersburg, iv, 1899, p. 49. 



