402 
Aug. F. Foerste 
had sagged (plate II, Fig. 1) on the death of the animal. Toward 
the upper part of the sloping surface, the peripheral area was 
broadly expanded by the tension. Toward the lower part of this 
sloping surface, the peripheral area of the Agelacrinus was dis- 
tinctly narrower, sometimes conspicuously so. The predominance 
of the cases in which the anal interambulacral area was directed 
toward the right side of the sloping surface suggests that the 
orientation preferred by the animal was one which would lift the 
anal area to about the same level as the oral aperture. The anal 
area is rarely directed either straight down or straight up the sloping 
surface, the latter being an extremely uncommon position. The 
location of the anal interambulacral area on the right side of the 
sloping support, is shown also by Agelacrinus holhrooki (plate I, 
Fig. ID). 
The reason for this orientation in the case of Agelacrinus pileus 
and Agelacrinus holhrooki, for the present, can be only a subject 
of speculation. It is noted, however, that among 22 specimens of 
Agelacrinus pileus, 5 rested upon valves of Rafinesquina having 
their anterior margins directed toward the lower part of the slope ; 
7 rested upon valves with their right anterior or left anterior 
outlines directed downward; and 6 rested upon valves with the 
lateral outlines directed downward, so that 18 out of 22 specimens 
rested upon valves having some part of the convex outline of the 
valve directed downward. This is the position which specimens of 
Rafinesquina should assume if occurring singly on sea bottoms 
swept by mild currents. In only 2, among the 22 specimens, was 
the anterior margin at the top of the sloping surface; and in the 
remaining 2 this margin faced diagonally upward. Here, again, 
the slope of the valves of Rafinesquina was determined by the 
direction in. which the theca of the Agelacrinus had sagged, on the 
death of the animal. 
If, now, it be assumed that the valves of Rafinesquina sloped 
toward the direction of the prevailing currents, some part of the 
convex outline facing the current, then the thecae of the Agela- 
crini, resting upon the same, usually would be oriented in such a 
manner as to prevent the excreta, escaping from the anus, from 
passing across the oral part, or across any considerable part of the 
area crossed by the ambulacral rays. 
It is probable, however, that the orientation of the animal was 
determined much more by the requirements for food, than by any 
