MOLLUSCA, 171 
of which is armed with numerous pyramidal teeth, with ir- 
regular summits, of a cartilaginous nature. The connection 
between these teeth and the integuments is so slender, that 
they are displaced by the application of the smallest force. 
They, however, project so far into the cavity, as to offer re- 
sistance to the progress of the food. There is yet another 
stomach, armed on the one side with deflected, pointed, car- 
tilaginous teeth. At the pyloric extremity are two mem- 
branaceous ridges, between which are biliary orifices, and 
the opening into a long narrow cecum, with simple walls, 
which is contained within the liver. The intestine is sim- 
ple, and after two turns ends in a rectum. ‘The salivary 
glands are very long, and, as usual, empty their contents 
into the pharynx. ‘The liver is divided into three portions 
by the folds of the intestine, each of which consists of seve- 
ral lobes. The biliary vessels are very large, and open at 
the mouth of the cecum into the last stomach. The food 
of the Aplysia consists of sea-weeds and minute shells. 
The circulating organs are remarkable. On each side 
the body, in the region of the dorsal plate, there is a large 
vessel, which receives blood from different parts of the body, 
and which likewise, by various openings, has a free com- 
munication with the cavity of the abdomen. In this respect 
there is a resemblance to the spongy, glandular bodies of 
the venze cavee of the Cephalopoda. These two vessels, or 
vene cave, unite posteriorly, and transmit their contents to 
the gills. The aérated blood is now conveyed to an auricle, 
of large dimensions, and uncommonly thin walls, situate be- 
neath and towards the front of the dorsal plate, and empty- 
ing its contents through a valve, into the right side of the 
ventricle. The aorta, which issues from the left and an- 
terior side, divides into two branches, the smallest of which 
