514 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
only on the folds (the smallest onl^- on the summit portion of them) 
and become slender, inconspicuous, or lost entirely on the interspaces, 
though many of them are continued in those spaces as very narrow 
vessels limiting the ends of the stigmata or crossing the latter without 
interrupting them. 
Development of a spiral arrangement of the stigmata and of infun- 
dibula confined to a row along the summit of each fold (indeed the whole 
upper portion of each fold may be described as composed of a row of 
infundibula), elsewhere the stigmata are straight or moderately curved 
and for the most part rather short, being more or less frequently 
interrupted or crossed by the transverse vessels already described. 
In general the direction of these stigmata is longitudinal (parallel 
to the length of the folds) though a tendency to curve toward the 
base of the nearest fold is conspicuous as the large transverse vessels 
are approached. The row of small infundibula along the ridge of 
each fold may be regarded as formed by the forking (twice) of larger 
infundibula of which there are generally two between adjacent trans- 
verse vessels of the first order. There are therefore generally eight 
of the small infundibula between two such vessels, but sometimes less 
or more. The spirals formed by the stigmata on these infundibula 
are more or less interrupted, and there does not appear to be any 
strict rule governing their direction; those of adjacent infundibula 
often but not always curve in opposite directions. Generally but 
one of the stigmata reaches the apex of an infundibulum. The 
internal longitudinal vessels are raised on high plate-like supports 
to bridge over these infundibula. 
The irregular network of internal supporting vessels which 
strengthen the sac in many species of this genus is not much developed 
in this form, perhaps because from the shortness of the stigmata the 
sac is fairly strong without such support. In some indiA'iduals, 
however, such supporting vessels are fairly- numerous in the dorsal 
part of the sac, and arise chiefly as branches of the regular transverse 
vessels. 
Stomach walls very thick, containing numerous comparatively 
small hepatic crypts or follicles which are visible on the exterior only 
as very low irregular prominences, somewhat suggesting the convolu- 
tions of the brain in their appearance. 
Intestinal loop very narrow, and nearly horizontal in position, the 
stomach and rectum forming nearly a right angle with the other part. 
