206 TRANSACTIONS OF THE [may 18, 
Type A, Plate XIV., Figs. a and 0. 
Oval plates, usually rather flat, having a strong ridge length- 
wise, and often a more obscure, obliquely transverse ridge. The 
form is not a true oval, and is usually more angulated on one 
side than the other. 
Size.—Length, 6 to 8 mm.; width, 4 to 6 mm. 
Type B, Plate XIV., Figs. ¢ and d. 
Semi-ellipsoid plates. These also are nearly flat and have a 
slight furrow along the straight side. From near the center at 
one side faint furrows radiate toward the rounded margin. Some 
of these plates have two long sides nearly parallel. 
Size.—Length, about 8 mm.; width, about 4 mm. 
Type C, Plate XIV., Figs e to h. 
Roughly semi-circular plates, with or without a flange on the 
straight side. Between the flange and the body of the plate is 
a deep furrow; body of the plate elevated and having an umbo 
which overhangs the furrow and from which a low ridge extends 
toward the rounded, often emarginate or obtusely pointed oppo- 
site margin. Usually the plate is depressed on one side of the 
keel and eleyated on the other, and there are sometimes obscure 
subsidiary ridges radiating from the main keel or ridge. The 
flange is usually wider at the sides, and reflected backward, or 
emarginated in the middle. These resemble the peripheral plates 
of Trochocystites, Barrande. 
Size.—Length, parallel to the furrow,5 to 8 mm.; width, 3 
to 5 mm. 
Type D, Plate XIV., Fig. 7. 
Ovate plates with pointed end. These have a distinct furrow 
along the axial line; they are convex all around, and have a 
short ridge inside near the apex. 
Size—Length, 6 mm.; width,5 mm. Rare. 
Type E, Plate XIV., Fig. k. 
Triangular plate rather flat, having ridges diverging toward the 
rounded corners ; ridges increasing in width and more prominent 
toward the outer ends. This plate may belong to a Cystidian. 
Size.—Length and width, 5 mm. Rare. 
Type F, Plate XIV., Figs. 1 and m. 
Sub-triangular plates, rather flat, with curved margins, one 
concave and the other convex. An arched furrow, nearer one 
margin than the other, traverses them.— Cirripodites cambrensis. 
Type G, Plate XIV., Fig. n. 
Triangular plates of high relief, sometimes showing facets of 
contact on the sides next the pointed end. One side of the plate 
rounded. 
Size.—Length, 4 to 5 mm.; width, 3 to 4 mm. 
