218 PSEUDOBONELLIA, A NEW ECHIUKOID GENUS, 



The Alimentary Canal. — The mouth is a wide ventral opening 

 at the junction of the body and proboscis. Behind, the buccal 

 cavity leads into a muscular pharynx that becomes continuous 

 with the irregularly coiled intestine, which in a specimen whose 

 body was about one inch long, was found to measure about four 

 inches in length (Plate ix., fig. 2). The intestinal contents are 

 arranged in oval pellets, probably by the muscular pharynx in 

 which food was seen to lie in a loose mass. 



The intestine is a rather thin-walled tube, consisting of a very 

 thin internal layer of circular muscle next to the enteric epi- 

 thelium, and surrounded by a slightly thicker layer of longi- 

 tudinal muscle. On the ventral region of the alimentary canal 

 the enteric epithelium is seen to be especially prominent ante- 

 riorly where the wall is thick, such modified structure being, 

 however, limited to about one quarter of the circumference of 

 this portion of the gut. Somewhat more posteriorly, where the 

 intestine is wider but thinner-walled, this modified part is much 

 more extensive, occupying at times about three-quarters of the 

 circumference of the ventral and lateral walls, but the layer is 

 then much less prominent. It appears to consist of a glandular 

 epithelium, and stains deeply with hematoxylin. No doubt the 

 structure is homologous with the ventral bandelette of some 

 French authors. 



Along its whole length the canal is attached to the body wall 

 by thin, muscular strands or " mesenteries," more prominent 

 posteriorly than anteriorly (Plate x., fig. 9). They are much less 

 numerous than those generally figured for B. viridis. A peri- 

 toneum lines the coelomic surface of the intestine. 



Lying dorso-laterally to the anterior region of the intestine is 

 a siphon, a delicate tube about 5 mm. long, in close connection 

 with the intestine, having in places a very narrow, compressed 

 bore, but whose lumen, in most parts, is wholly obliterated. No 

 definite opening into the pharynx exists. The siphon arises as 

 a thickening on one side, more or less dorsally, soon becoming 

 distinct from the pharyngeal wall, but remaining in close associa- 

 tion with it, being separated merely by a very narrow, membrane- 

 like tissue. After maintaining contact for some distance, it 



