192 PROCEEDINGS OF THE ACADEMY OP 



it entirely. The last two autliors figure a retractor to the duet of 

 the genital bladder, and so does Leidy (though in the description 

 of the plates he refers it to tiie vagina). Lehmann figures a re- 

 tractor also to the genital bladder itself. Lehmann's figure of the 

 genitalia of A. fuscus (pi. VI., fig. 2) agrees more closely with 

 Leidy's figure in all respects, indee(^ but the position of the 

 retractor penis, which Lehmann places at the top of tlie penis sac. 

 His figure of the dentition of fuscus is nearer mine of the Boston 

 specimens than is his of hortensis, though the transverse count of 

 teeth is larger. Goldfuss' figure of the dentition of A. hortensis 

 also (1. c. pi. v., fig. 6) differs from my figure in tlie 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 geni- 

 talia whether to refer our species to fuscus or hortensis, though I 

 incline to the former. From the dentition I should assuredly adopt 

 the former name also. 



The jaw of the Boston specimen (pi. XVI., fig. 2) is thick, 

 arcuate, ends but little attenuated: no median projection to the 

 cutting edge: anterior surface with 8 stout, separated, unequal ribs, 

 denticulating either margin. 



Lingual membrane (pi. V., fig. 5) long and narrow. Teeth about 

 31 — 1 — 31, with about ten 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 the base of attachment, beyond which projects 

 the stout cutting point: side cusps distinct, but small, with dis- 

 tinct, small, stout cutting points. Laterals like the centrals, but 

 unsymraetrical by the suppression of the inner, lower, lateral ex- 

 pansion 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. 



My figure a shows one central with its adjacent lateral, and b 

 and c marginals, the latter form near the outer margin of the 

 membrane. 



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

 Limax, Zoyiites, and others, tiie lateral teeth are either bicuspid 

 or tricuspid. The number of cusps does not seem a generic 

 character. 



