96 A MANUAL OF AMERICAN LAND SHELLS. 



well marked, calcareous, subhexagonal, longer than wide. In the 

 specimen of A. Colmnbianus there were decided concentric lines of 

 growth on the shell, as w411 be seen below in my figures, also in Ander- 

 soni and HempMlK. 



The caudal mucus pore was plainly visible in all the specimens of A. 

 niger which I have examined. In Fig. 64 I have figured the pore of 

 this species. It seems to be in two portions, one erect, triangular, at 

 the end of the body of the animal, with another running at right angles 

 with it in a gutter-like excavation towards the extreme end of the tail. 

 In A. Colunibianus and A. Andersoni the pore was quite different from 

 this, as seen in Figs. 61, 67. In this the erect portion of the pore is en- 

 tirely wanting, the carinated body being arched regularly down to and 

 overhanging the foot. The longitudinal gutter like pore is, however, 

 plainly visible. In numerous specimens of A. Calif or nicus the body is 

 also arched down to, and overhangs the foot. On the tail, corresponding 

 to the gutter-like pore of the last-mentioned form, there was no sign of 

 any pore, but in its place the flesh was sponge-like, without the mark- 

 ings which are found on the neighboring portions of the foot. It may 

 be, therefore, that in these specimens the mucus pore was contracted 

 or closed. No doubt it exists in the living animal, as I have had the 

 opportunity of seeing it there, in other individuals. 



Of the internal anatomy I have examined the nervous system in 

 both A. Galifornicus and A. Gohimhianus. The ganglia present the 

 usual three sets, all globular in form, and so crowded together in the 

 suboesophageal and superoesophageal as almost to form a continuous 

 chain around the buccal mass. 



In these same two forms, also, I have examined the circulatory and 

 respiratory organs. Within the respiratory cavity is a large, spongy, 

 ear-shaped organ, attached only at one point to the roof of the cham- 

 ber. This I suppose to be the renal organ, surrounding, and indeed 

 inclosing, the heart, though it is not so arranged in any of the genera 

 described by Dr. Leidy. In Arion hortensis he describes the nearest 

 approach to such an arrangement. 



I have examined the digestive system of all the forms and figured 

 (Pr. Phil. Ac. N. S., 1874) that of both A. Galifornicus and Golum- 

 bianus. In the latter (PI. II, Figs. D, F, referred to) the buccal mass 

 (1) is large and round, the salivary glands (4) short and broad; the 

 stomach (5) long and large, with a decided constriction at its middle, 

 and the usual cul-de-sac (6) at its extremity, at which point the biliary 



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