ARIOLIMAX. 229 



it with specimens from more northern regions, whence the species was origi- 

 nally described, but I have now verified the identity of this form, having received 

 it from the original locality. 



In treating these various forms, 1 I have abstained from giving any descrip- 

 tion of their exterior markings. Such description would be unreliable, as the 

 specimens have been long preserved in alcohol, 2 and are evidently in various 

 degrees of contraction. I will say, however, that I found in all the blind sac 

 under the mouth (well marked, though not very deep), which is suspected by 

 Dr. Leidy to be the seat of the olfactory nerve. 



I can also here refer to several external characters not affected or obliterated 

 by contraction in alcohol. All the specimens have a distinct locomotive disk 

 to the foot. In all, the orifice of respiration is decidedly posterior to the 

 middle of the right margin of the mantle. The position of the anus I found in 

 A. Columbianus to be posterior and inferior to the respiratory orifice, with a 

 gutter-like groove to the edge of the mantle. The position of the orifice of the 

 generative organs is not so easily decided in alcoholic specimens. I have no 

 doubt, however, that in the living animal it is under the mantle, not close be- 

 hind the right tentacle. In one form, Ariolimax Californicus, there are beyond 

 doubt two distinct orifices; that of the male being smaller and anterior. In 

 Dr. Cooper's figure of A. Californicus (Proc. Phila. Acad. Nat. Sci., 1873, 

 PI. III. Fig. D, 3) the two orifices are plainly shown, and suggested to me 

 the identity of my specimens with his species, especially as the external mark- 

 ings also agreed with his description. In A. Columbianus also there is no 

 common duct or cloaca, as Dr. Leidy calls it, to the genitalia, though I could 

 not detect more than one exterior orifice. In A. niger there can be but one 

 common orifice, judging from the penis entering into the common cloaca, as 

 shown in Fig. F of PL XII. The same may be said of A. Hemphilli and 

 A. Andersoni? 



The mantle is free on its margin in its whole circumference, especially in 

 front and on its sides as far back as the respiratory orifice. I could detect no 

 concentric lines or other markings on the mantle. The mantle was greatly 

 produced and swollen on its margins in Mr. Steam's specimen of A. Cali- 

 fornicus, In that and all the specimens examined I found an internal shell, 

 varying somewhat in thickness, but always well marked, calcareous, sub-hex- 

 agonal, longer than wide. In the specimen of A. Columbianus there were 

 decided concentric lines of growth on the shell, as will be seen below in my 

 figures, also in Andersoni and Hemphilli. 



The caudal mucus pore was plainly visible in all the specimens of A . niger 

 which I have examined. In Fig. 133 I have figured the pore of this species. It 

 seems to be in two portions, one erect, triangular, at the end of the body of the 



1 I have also examined A. Hemphilli and A. Andersoni? Thus I have had opportuni- 

 ties of examining authentic, specimens of all our species. 



2 Since the above was written, I have received all the species alive. 



