230 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



animal, with another running at right angles with it in a gutter-like excavation 

 towards the extreme end of the tail. In A. Columbianus and A. Andersoni 

 the pore was quite different from this, as seen in Fig. 130. In this the erect 

 portion of the pore is entirely wanting, the carinated body being arched regu- 

 larly down to, and overhanging the foot. The longitudinal gutter-like pore is, 

 however, plainly visible. In numerous specimens of A. Californicus, 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 markings 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, and lately I have had the opportunity of seeing 

 it there. 



Of the internal anatomy I have examined the nervous system in both A. 

 Californicus and A. Columbianus. The ganglia present the usual three sets, 

 all globular in form, and so crowded together in the subcesophageal and 

 superuesophageal as almost to form a continuous chain around the buccal 

 mass. 



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

 tory organs. Within the respiratory cavity is a large, spongy, ear-shaped 

 organ, attached only at one point to the roof of the chamber. This I suppose 

 to be the renal organ, surrounding, and indeed enclosing, the heart, though it is 

 not so arranged in any of the genera described by Dr. Leidy. In Arion hor- 

 tensis he describes the nearest approach to such an arrangement. 



I have, examined the digestive system of all the forms, and figured (1. c.) 

 that of both A. Californicus and Columbianus. In the latter (PI. II. Fig. 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 

 ducts (7, 7) enter; from this the stomach passes into the intestine (8), which 

 proceeds first forward almost to the oesophagus, thence proceeds backward to 

 the extreme rear of the general cavity of the body, and again forward to below 

 the respiratory cavity, into which it penetrates upwards as the rectum (9), and 

 through which it passes to the anus, whose position is described above. The 

 intestine in its whole course winds among, and is imbedded in, the various 

 lobes of the liver, which latter organ is arranged as usual in Limax, Arion, 

 etc. 



In A. Californicus (PI. XI. Fig. E, 1. c.) there is a difference in the arrange- 

 ment of the stomach. P>efore reaching the cul-de-sac (6), the stomach is 

 greatly constricted, and the eul-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 

 connection was entirely concealed by the cul-de-sac in its upright position. 



