FAUNA OF THE TRENTON GROUP. 
3 
Horizon and Locality . This form is fairly common in the 
“crinoid beds” near the liftlock at Kirkfield, where specimens have 
been collected by W. A. Johnston, E. J. Whittaker, and the writer. 
A large slab with many specimens was collected by Dr. R. Ruede- 
mann and is now in the New York State Museum., 
Genus, Amygdalocystites Billings. 
Amygdalocystites radiatus Billings. 
Plate IX, figures 5 — -7. 
Amygdalocystites radiatus Billings, Can. Jour. 2, 1854, p. 271, 
figs. 7, 8. 
Eor later references, see Bassler’s Bibliography of Ordovician 
and Silurian fossils. 
The braehioles of this genus have not, it is believed, been 
illustrated, though Bather has indicated them in outline in one of his 
figures. 1 Two specimens found by the writer on a large slab at Healy 
falls, Trent river, show the remains of some of them. They prove 
to have been fairly long, slender, and apparently flexible organs, and 
seem to have a structure similar to those of Pleurocystites. The 
lower portion is made up of long plates, those on the two sides being 
opposite in position instead of alternating as in Pleurocystites , and 
the groove so formed' is roofed by numerous small covering-pieces, 
those on opposite sides dove-tailing into each other. The lower plates 
are rather long* and there are about fifteen covering plates to five of 
the lower ones. The arrangement of the plates opposite to each other 
instead of alternating and so dove-tailing into the lower surface 
produces greater flexibility but results in less strength, which probably 
explains why the braehioles are not seen more often. The best- 
preserved braehioles are a little over 10 mm. long. As will be noted 
in the figure, a part of them bend upward and those above downward, 
thus indicating the position of the mouth of this individual. Another 
Specimen shows the anal pyramid, which is composed of a circle of 
eight plates. 
A specimen of Amygdalocystites florealis Billings collected by 
Mr, Whittaker at the liftlock shows the bases of several braehioles 
apparently similar to those already described, though perhaps a trifle 
stouter and with shorter plates (Plate II, figure 4). 
Each specimen shows a small piece of column. Near the prox- 
imal end, at least, the column proves to be made up of alternating 
columnals, there being, however, very little difference in the diameters 
VLankester, E. R., A treatise on zoology: Part 3, The Echlnodermata 
By P. A. Bather, 19 00', p. b'7, fig'. XIX, 1. 
10711— H 
