Norwegian Solenogastres. 27 
At the rear end of the animal, above the cloacal cavity, the 
cuticula is interrupted by a deep cylindrical pit serving as a sen- 
sory organ. Its fundus is lined with cylindrical cells apparently 
forming a glandular mass, and being in connection with the 
lacunar tissue at the base of the median branchial fold. 
Alimentary canal. In front, and at the sides, of the mouth 
the cirrus sac is situated as usual, bearing numerous short and 
crowded cirri (fig. 37), and separated from the atrium of the 
pharynx by means of well developed oral lists. The pharynx 
succeeding the atrium is rather narrow, and has its walls folded 
longitudinally. Beneath the cylindrical epithelium lining of the 
pkarynx a thick, glandular mass appears, representing a dorsal 
salivary gland which opens into a small projection of the phar- 
yngeal wall. Farther back, the pharynx widens again and from 
its lateral sides a broad fold projects inwardly; the folds finally 
join medially, with their under corners thus separating the lower 
portion of the pharynx from the upper one so as to form a small 
coecum; behind it the folds are clothed with the tooth-bearing 
cuticula which forms the radula. Just at the anterior end of the 
radula and at its upper side the ducts of the ventral salivary 
glands open. Somewhat behind this point a narrow oesophagus 
leads dorsally into the intestine. 
The radula presents the distichous type; the two lateral folds 
of the pharynx continue backward forming between them a median 
furrow. The sides have their cuticula differentiated in erect 
isolated stripes with a dorsoventral extension and an extremely 
fine serration of their margins. Farther back, behind the oesoph- 
agus, the basal plates grow thicker with larger denticuli; here 
moreover the radula is entirely covered medially with an epithe- 
lium. This covering evidently serves as the matrix of the denticles; 
its celis are cubical with rounded nuclei, while the basal mem- 
brane is a product of the underlying mostly cylindric epithelial 
cells with prolonged nuclei. 
In examining the frontal end of the radula we will find that 
the transversal ridges representing the teeth not only occur on 
the medially turned sides of the pharynx, but that their substratum 
is bent outwardly, so that the teeth of each side appear at two 
points in the section. Immediately below the openings of the 
Salivary glands a pair of lateral diverticula of the pharynx issue 
towards behind, and the radular cuticula passes into them. In 
