1'ELONAIA, A NEW GENUS OF TUNICATED MOLLUSKS. 437 



The oesophagus commences by a white plicated opening at 

 the lower end, and on one side of the sac. It is curved in a 

 sigmoidal form, and exhibits longitudinal rugae through its 

 coats. Near the lower end of the mantle cavity, it terminates 

 by suddenly dilating into the stomach, which is pear-shaped, 

 and directed obliquely upwards towards the side opposite to 

 the oesophagus. The internal surface of the stomach presents 

 longitudinal plicaB, and is succeeded by the intestine, which 

 at first curves upwards, then down to the bottom of the mantle 

 cavity, up along the oesophageal side of that cavity, and be- 

 tween its walls and the branchial artery, terminating about 

 the anterior third of the animal in a funnel-shaped anus, which 

 is cut into ten or eleven processes like the petals of a flower. 

 The first part of the intestine is white and longitudinally 

 plicated ; the rectum is dilated with attenuated coats. 



3. Vascular System. — The vascular system resembles that 

 of the true Ascidice, except that there is no heart. It consists 

 of two sets of vessels, with four sets of capillaries, a circle 

 in fact twice interrupted, once in the respiratory sac, and 

 again throughout the body. The branchial veins run along 

 the transverse plaits of the sac, receiving secondary and ter- 

 nary twigs at right angles. The primary branchial venous 

 branches empty themselves on each side into the branchial 

 venous trunk, which runs in the substance of the double cord 

 which coasts the superior aspect of the sac. This double cord 

 terminates in an abrupt manner anteriorly near the oral ori- 

 fice, and in a similar manner, but after becoming smaller, near 

 the orifice leading to the cesophagus. At this point the vein 

 becomes an artery, and probabbj sends back vessels to nourish 

 the sac. It now runs along the cesophagus, supplying the 

 stomach and intestine, and giving off in its course branches 

 to the cloak. The veins arising from the arterial capillaries 

 of tin; body meet near the commencement of the (esophagus 

 in one trunk, which, passing along the inferior wall of there- 



