346 PROCEEDINGS OF THE ACADEMY OF [1896. 



from the humid British Columbian region, in which melanism is of 

 common occurrence in snails, birds and mammals. In a series of 

 several hundred examples we find great variation in the extent of 

 the black marking. 



We hazard little in assuming that "A. Californieus forma macula- 

 tus" Ckll. is identical with the spotted form of Columhianiis, and has 

 nothing whatever to do with the true A. Californieus Cooper. Like 

 a good many " varieties " of slugs, this is " such stuff as dreams are 

 made of." 



•We have opened numerous spotted Californian Ariolimaces, and 

 found them invariably to have the extremely characteristic genitalia 

 of Cohimbianus. Proof that a spotted form occurs in the other species 

 is lacking. 



A. Columbianus var. stramineus Hem]iliill. PI. XII, fig. 1. 



Alcoholic specimens clear, light buff. Length 59 ; greatest breadth 

 (across shield) 19 ; greatest width of sole 15 mm. Genitalia as in 

 typical A. columbianus. 



Habitat : Santa Cruz Island, California. 



The specimen figured is one of Hemphill's original lot. 



A. Californieus Cooper. PI. XIII, figs. 5, 6 ; PI. XIV, figs. 14-16. 



Ariolhnax Californieus J. G. Cooper, Proc. Acad. Nat. Sci. Phila., 1872, 

 p. 146, pi. 3, f. D, 1-3. W. G. Binney, Proc. Acad. Nat. Sci. Phila., 1874, p. 

 83; Am. Lye, N. Y._,_X, 1873, p. 297 ; Terrest. Moll., V. p. 232, pi. v, fig. F 

 (dentition), and pi. xii, f. D (genitalia); Man. Amer. Land Sh., p. 99 f. 62, 

 63; Third Suppl. Terr. Moll., V (Bull. M. C. Z., XIX, No. 4), p. 211, pi. v. 

 f. E (living animal) and f. H (penis). Simroth, Nova Acta Acad. Caes. Leop. 

 Carol. Germ. Nat. Cur., LVI, 1891, p. 365, pi. 7 [xv], f. 9-11 ; Malak. Blat- 

 ter (n. F.)XI, pl.l, f. 5. 6. 



Distribution : We have seen this species from San Mateo Co., 

 California, only. 



Color of alcoholic specimens brownish ochraceous, sole gray ; foot 

 margin uniform with the upper surface, or dusky with vertical dark 

 lines. 



The free anterior portion of mantle is shorter than in A. Colum- 

 bianus, less than one-fourth the entire length of the mantle. 



Jaw (PI. XIV, fig. 13) with about 9 ribs, denticulating both mar- 

 gins. 



Radula (PI. XIII, figs. 5, 6) with the formula 67.1.67. Rhachid- 

 ian teeth with well developed side cutting-points ; mesocone long, 

 reaching to posterior edge of basal plate. Inner lateral teeth, without 

 inner cusps, otherwise similar ; outer laterals becoming oblique, with 

 Jong mesocones, the ectocone gradually reduced to a slight sinuation. 



