456 
Aug. F. Foerste 
the theca; subclavate in outline, with the greatest width, 1 mm., 
not at mid-length, but about one-third of the length of the ray 
from the end. This sub-clavate outline is noticeable especially in 
the case of the anterior ray, opposite the anal area. The posterior 
rays, on each side of the posterior interambulacral area, branch 
off not from the center of the theca but from near the base of the 
lateral rays, on their posterior sides, thus producing wider interam- 
bulacral spaces between the proximal ends of the posterior rays 
than between any of the other rays. Only the lateral covering 
plates are visible along the rays; nine or ten on each side of the 
anterior ray, seven or eight on each side of the lateral rays, and 
eight on each side of the posterior rays. These covering plates are 
slightly imbricated and their tips alternate along the median line 
of the rays. Interambulacral plates about as numerous as in 
Hemicystites stellatus. Anus nearer the central part of the poste- 
rior area than indicated in the published figures of that species. 
Upper part of the margin strongly reenforced by large flat plates, 
the lower margins of which slope gently toward the center, 
only their upper edges being exposed exteriorly. 
On comparing these specimens with Hemicystites stellatus, little 
is found to distinguish them. Compared with the type of that 
species, the rays are narrower and less elliptical, and the interam- 
bulacral areas are correspondingly wider. The trimerid origin 
of the rays also appears to be more in evidence, owing to the wider 
separation between the posterior rays. A wider acquaintance with 
the range of variation of Hemicystites stellatus is likely to decrease, 
rather than increase, the supposed differences of H. carnensis. 
The number of Fairmount forms represented by closely similar 
precursors among Trenton species is a matter of interest, and this 
number is continually increasing. 
Description of Several Lepadocystinae 
40. The Migration of the Anus of the Glyptocystidae 
Bather, in his treatise on the Echinoderma, in 1900, and again in 
his CaradocianCystideafrom Girvan, Figure 45, in 1913, determined 
the probable path of the gut along the inner wall of the theca in 
the primitive Glyptocystidae by noting where the gut pore-rhombs 
failed to appear in any known species. The second figure is re- 
