ARION. 



still exists there, 1 specimens having been found by me in 1871, from one of 

 which I extracted the jaw and lingual membrane here described. I have com- 

 pared the figures of the genitalia of A. hortensis given by Lehmann and A. 

 Schmidt 2 with those given by Leidy in Terr. Moll. U. S. There is a differ- 

 ence in the position of the retractor muscle of the penis. Leidy places it at 

 the base of the penis sac, Lehmann at the top, Schmidt omitting it entirely. 

 The last two authors figure a retractor to the duct of the genital bladder, and 

 so does Leidy (though in the description of the plates he refers it to the vagina). 

 Lehmann figures a retractor also to the genital bladder itself. Lehmann's 

 figure of the genitalia of A.fuscus (PL VI. Fig. 2) agrees more closely with 

 Leidy's figure in all respects, indeed, but the position of the retractor penis, 

 which Lehmann places at the top of the penis sac. His figure of the dentition 

 offuscus is nearer mine of the Boston specimens than is his of hortensis, though 

 the transverse count of teeth is larger. Goldfuss's figure of the dentition of A, 

 hortensis also (1. c. PL V. Fig. 6) differs from my figure in the same way, i. e. 

 by the presence of an inner side cusp and cutting point to the lateral teeth. 

 Thus I find it impossible to decide from the genitalia whether to refer our 

 species tofuscus or hortensis, though I incline to the former. From the denti- 

 tion I should assuredly adopt the former name also. 



The jaw of the Boston specimen (Fig. 1 2 7) is thick, arcuate, ends but little atten- 

 uated ; no median projection to the cutting edge ; anterior surface with 8 stout, 

 separated, unequal ribs, denticulating'either margin. 



Lingual membrane (PL V. Fig. C) long and narrow. Fig. 127. 



Teeth about 31 1 31, with about 10 perfect laterals. 

 Centrals with the base of attachment longer than wide: 

 reflection half as long as the base of attachment, bearing 

 one long, stout cusp extending to the lower margin of Jaw of A. 



the base of attachment, beyond which projects the stout 



cutting point ; side cusps distinct, but small, with distinct, small, stout cutting 

 points. Laterals like the centrals, but asymmetrical by the suppression of 

 the inner, lower, lateral expansion of the base of attachment, and the inner 

 side cusp and cutting point. The marginals are low, wide, with one long, 

 bluntly pointed, oblique cutting point, bearing a subobsolete smaller point low 

 down upon its outer side. This subobsolete side cutting point is on some of the 

 marginals much more developed. 



From the above remarks it will be seen that in this genus, as in Limax, 

 Zoniles, and others, the lateral teeth are either bicuspid or tricuspid. The 

 number of cusps does not seem a generic character. 



Tin; internal calcareous grains which represent the shell are in some species 

 isolated, in others aggregated into a nearer resemblance to the internal plate 

 of Limax. On this distinction are based the subgenera Loche.a and Prolepis. 



1 Specimens can readily be found in gardens between Chestnut and Mt. Veruon Streets 

 above Willow Street, as well as elsewhere. 



2 Der Geschlechtsapparat der btylomniatophoren, 1855. 



