30 PROCEEDINGS OF THE ACADEMY OF 



various lobes of the liver, which latter organ is arranged as usual 

 in Limax, Avion, etc. 



In A. Calif amicus (plate XI. fig. e), there is a difference in the 

 arrangement of the stomach. Before reaching the cul-de-sac (6), 

 the stomach is greatly constricted, and the cul-de-sac runs at 

 right angles with the stomach in an erect position, not lying on 

 its side as I have represented it, in order to show the connection 

 between it and the anterior portion of the stomach, which connec- 

 tion was entirely concealed by the cul-de-sac in its upright posi- 

 tion. The extreme length of the digestive system is three times 

 that of the whole body of the animal, at least in its contracted 

 state. 



The jaw in all the forms of Arioliviax is quite thick, dark horn- 

 colored, arcuate ; ends but little attenuated, blunt ; anterior surface 

 with stout ribs, denticulating either margin. I have figured the 

 jaw of A. Golvmhianus'^ (plate II. fig. h) which has about twelve 

 ribs. In A. Californicus, from Mr. Anthou}-, there were thirteen 

 ribs to the jaw; fourteen in Mr. Hemphill's specimen of the same. 

 In A. niger Dr. Cooper describes about twenty, but in one spe- 

 cimen I found but eight. In Land and Fr. w. Shells, I. p. 280, I 

 have figured a jaw of the true northern form with eighteen ribs. 



The pouch of the lingual membrane is shown in plate II. fig. 

 D, 5. The membrane is as usual in the Helicidae, with tricuspid 

 central, bicuspid lateral, and quadrate marginal teeth showing 

 simply a modification of the laterals. In L. and Fr. w. Shells, I. 

 ]). 280, I have figured the lingual membrane of the true northern 

 A. Columbianus. The marginal teeth are there shown to have 

 one long denticle and a small, subobsolete side denticle. This 

 form of marginal teeth I have found in the form I have referred 

 to ^'^. Columbianus? (see plate II. fig. e). Also in one of Dr. 

 Cooper's tj'pes of A. niger (plate XI. fig. a), and in both the spe- 

 cimens of A. Californicus (plate XI. fig. g). This form of mar- 

 ginal tooth may therefore be considered characteristic of the 

 genus, though in one specimen supposed to be A. niger, I noticed 

 marginal teeth with the outer cusp much more developed and 

 bifid, and figured them in Ann. Lye. N. H. N. Y., x. pi. xiii. fig. L 

 In plate XI. fig. B, I have given the central and the adjoining 

 lateral teeth of A. niger. In fig. F, the central and one adjoining 

 lateral of A. Californicus. 



There is no retractor muscle to the buccal mass in A. Califor' 



