470 
Aug. F. Foerste 
Memorial Museum, at Ottawa, and forms the basis of the fol- 
lowing very full description. 
Plates arranged as in the following diagram. 
Fig. 8. Diagram of Brockocystis teciwiseihi, Billings. The outlines of plates 
20-24 could not be determined with accuiacy. The outlines of the hemispheri- 
cal protuberances are indicated. Specimen No. 8447, in the collections of the 
Geological Sui vey of Canada. 
The plates of the fifth row are practically concealed under the 
plates belonging to the ambulacral or subvective system. There 
apparently is a trace of the outline between deltoid 23 and plate 
18, but the remainder of the outline of plate 23 is not known and 
no deductions must be drawn from the outline of this plate in the 
diagram, which represents merely the space between the overlap- 
ping ambulacra. The plates bearing the large hemispherical protu- 
berances are indicated in the diagram. Those on plates 1 and 13 
are small. Those on plates 2, 3, 4, 14, 16, and 17 are of medium 
size. The remainder are large. No protuberances occur on 
plates 18, 19, or 15, excepting the triangular supports for the 
ambulacra. On these three plates, also, the reticulate ornamen- 
tation is faint or obsolete. 
Pectinirhombs more or less discrete along the suture lines 
separating the two plates forming the rhomb. The lower bound- 
ary of the rhomb on plates 12, 14, and 10 is strongly defined by a 
vertical wall formed by the adjacent part of the hemispherical 
protuberances on these plates. The upper part of the stereom-fold 
area on the same plates also is sharply defined, but only by a sharp 
striation. The boundaries of the fold areas on plates 15 and 18 
are distinct, but not defined by conspicuously elevated striae or 
walls. The pectinirhomb on plates 1-5 is strongly defined by a 
vertical wall along its upper outline on plate 5, it is strongly 
