ARIOLIMAX. 227 



generation on the right of the body, below the anterior, free part of the mantle, 

 distinct but contiguous (in A. Californicus, certainly), that of the male organ 

 anterior. Tail furnished with a perpendicular, triangular mucus pore, with a 

 horizontal mucus slit to the end of the tail. 



Testaceous plate flat, thick, calcareous, simple, not spiral ; longer than wide, 

 hexagonal. 



Inhabits the Pacific Province, on the Pacific Coast of the United States, at 

 least from latitude 34° to 49°, apparently not eastward of the Sierra Nevada 

 and Cascade Ranges'. 



The species on which the genus was founded has been known for many years 

 as a Lbnax (see Gould in Terr. Moll. U. S., II., III. and Ex. Ex. Mollusca, 

 where an additional figure is given), but it was not until 1859 that Morch (Mai. 

 Bliitt. VI. 110) recognized it to be distinct from Limax and proposed a generic 

 name, Ariolimax. In 1865, W. G. Binney (Amer. Journ. Conch., I. p. 48, PI. 

 VI. Figs. 11-13) gave a more detailed generic description, adding figures of 

 jaw and lingual dentition. These were also given in Land and Fresh-Water 

 Shells N. A., I. p. 278, Figs. 496-498 (1869). As late as 1868 the species is 

 still retained in Lbnax by Tryon (Amer. Journ. Conch. III. 315), who gives a 

 copy of one of Gould's figures from the Terrestrial Mollusks. 



The genus has affinities with, but is readily distinguished from Limax, Anon, 

 and Prophysaon. It agrees with Limax in having an internal shelly plate, in 

 the position of its respiratory orifice and its distinct locomotive disk ; but it 

 differs in having a caudal mucus pore, a ribbed jaw, quadrate (not aculeate) 

 marginal teeth on the lingual membrane, and in the position of its genital ori- 

 fice. With Arion it agrees in having a mucus pore, a distinct locomotive disk, 

 a ribbed jaw, in its lingual membrane, and position of the genital orifice ; but 

 it differs in the position of its respiratory orifice and its internal shell. With 

 Prophysaon it agrees in having an internal shell, a ribbed jaw, in its lingual 

 membrane ; but differs in the position of the genital and respiratory orifices, in 

 its distinct locomotive disk and caudal mucus pore. 



From the other sluglike, or semi-sluglike American genera, Tebennophorus, 

 Pallifera, Binneya, Ilemphillia, Veronicella, it is most readily distinguished. 



Jaw thick, slightly arcuate, ends but little attenuated, blunt; low, wide; an- 

 terior surface with numerous stout ribs, denticulating either margin. The 

 number of ribs varies in the several species, and in 

 different individuals of the same species. Fig. 128, 

 drawn from the true northern A. Colutnbianus, has 18 

 ribs ; another specimen, supposed to be the same spe- 

 cies, has about 12. (See Proc. Acad. Nat. Sci. Phila., Jaw of Ar , n i, max 

 1874, PL II. Fig. 11.) A. Californicus has given 13 Columbians. 

 and 14 ribs. A. niger has been described by Dr. Cooper 



with 20, but I found only 8 in one specimen which I refer to that species. In 

 A. Hemphilli there are from 8 to 12 ; in H. Andersoni? there are 13 ribs. 



