40 Nils Hj. Odhner. 
are 22 teeth in a transverse row of the radula, whereas D. sarsi 
has 16, but it is probable that the number is not specifically 
constant (cf. Simrothiella). Further there are differences in the 
shape of the shell gland, the paired portions of which in D. sarsi 
are tubular and provided with each a somewhat widened ampulla 
on the median side, whereas in D. acuta the proximal tubes are 
more inflated and apparently lack the ampulla.*) Also in the 
structure of the pharynx and the intestine there are some slight 
discrepancies: in D. acuta the large pharyngeal sphincter is much 
stronger than in the present species, and the intestinal dorsal 
coecum does not extend in front of the brain. 
It is beyond all doubt that the original specimen of Solen- 
opus sarsi though now deprived of the both extremities of the 
body where the most characteristic markings are to be found, 
can be referred to the genus Dorymenia, and that it is specific- 
ally identical with the forms on which the above description is 
based. There is in fact the closest correspondence between the 
prototype and the latter inter alia in the structure of the cuticula, 
the ventral muscles and the horizontal septum of the ventral 
vessel, as well as in the formation of the ova, facts which could 
be established on transverse sections. For this species, which 
together with Solenopus margaritaceus was previously included 
by HANSEN in Proneomenia, a distinct subgenus was created by 
PiLsBry (1898) in view of the simultaneous presence of a radula 
and of gills in the shape of longitudinal folds. The latter are, 
however, in reality entirely absent in the present species. It is 
true that HANSEN (1888) establishes the occurrence of gills in 
S. sarsi, as well as in S. margaritaceus, and that he even gives 
two figures in illustration of this feature (figs. VIII and IX). 
There can be no doubt that these figures have reference to the 
present form; this is evident from the drawings of the cuticula. 
Yet the figures in question must be considered as misleadingly 
interpreted by HANSEN. In view of the indubitable fact that gills 
are entirely absent I cannot explain the figures in question other- 
wise than as representing a section through the anterior, instead of 
the posterior, end of the animal, and showing the oral cirri. 
Many similar figures in HEatH’s work as well as sections of other 
species, bear out this view. HANSEN is correct in stating that it 
7 1) This may, however, perhaps be due to a state of less developed sexual 
maturity. 
