282 NEW YORK STATE MUSEUM 



anterior portion of the animal, the large artery, which supplies 

 the stomach, gives origin to a comparatively large branch to the 

 digestive gland, and gives off numerous branches, both to the 

 intestines and digestive gland. The next branch proceeds from 

 the same side of the artery, continuing to the digestive gland, 

 giving off numerous branches and finally forming a network in 

 the lobes of the digestive gland (pi. 18, fig. 9). 



The next branch is from the opposite side of the artery, and con- 

 tinues on the posterior part of the stomach. This branch is prom- 

 inent. At about one half the distance from the artery to the ven- 

 tral part of the stomach it bifurcates, one branch again bifurcat- 

 ing; one branch containing latero-anteriorly and the other dorso- 

 anteriorly. The main branch continues to the ventral part of the 

 stomach, bifurcating; the branches continuing mainly on the ven- 

 tral part of the stomach. 



The next prominent branch is from the opposite side of the ar- 

 tery. The principal artery of this branch continues to a lobe of 

 the digestive gland, and ramifies through it; a smaller branch con- 

 tinues to the intestine. 



The next conspicuous artery is from the large artery which sup- 

 plies the uterine canal and the so-called prostate gland. 



Pulmonary cavity. The pulmonary cavity lies below the mantle 

 and is of essentially the same shape. It is situated immediately 

 below the shell cavity, and contains the heart, renal organ, the 

 posterior part of the rectum and the anus. It is separated from 

 the visceral cavity by the muscular peritoneum or diaphragm.^ 



The respiratory orifice is situated on the right side of the body, 

 at the edge of the mantle (pi. 23, fig. 1, 1). This orifice opens and 

 closes at regular intervals; the normal respiration seems to be 

 from 16 to 18 times a minute, though it is frequently variable. 

 When open the orifice is circular, and is closed by muscular fibers 

 which surround it. 



The pulmonary veins, or rete, are situated mostly on the roof of 

 the cavity. They are numerous, anastomosing, and occupy nearly 

 the whole surface (pi. 19, fig. 2). 



Veins. The veins are situated mostly in the substance of the 



