204 PALEOZOIC PALEONTOLOGY. 
globose and is the most prominent of the three; the posterior lobe is 
a little more prominent than the anterior. The entire surface, except 
im the furrows and on the marginal border, is finely papillose. 
The dimensions of the type specimen are: length, 3 mm.; height, 
1.8 mm. 
BEYRICHIA BARRETTI N. sp. 
Plate NEXShhie Hiss 9: 
Description.—This species resembles the last, but is smaller, with 
the anterior furrow narrower and with the posterior one produced 
further toward the ventral margin, giving to the median'lobe a more 
elliptical outline. The surface is also very differently marked, it 
being covered with rather large, irregular pits. The ventral margin 
is nearly straight in the central portion, the anterior and posterior 
exiremities of the valve being of nearly equal height. 
The dimensions of the type specimen are: length, 2.3 mm.; height, 
1.5 mm. 
BEYRICHIA PERINFLATA ND. Sp. 
Plate XXIII., Wig. 6. 
Descriptwon.—Carapace subelliptical in outline, highest in front, 
greatly inflated antero-ventrally. Hinge-line straight, about four- 
fifths the total length. The free margin, from the postero-dorsal 
angle to the middle of the ventral margin, with a depressed marginal 
border, which is concave within, with a rounded ridge externally, 
outside of which the surface drops vertically to the edge of the valve. 
In the anterior half of the valve the marginal border is covered by 
the strong inflation of the body of the valve. Valves divided by two 
vertical furrows from the dorsal margin; posterior furrow beginning 
at about the middle of the hinge-line and extending nearly vertically 
downward to beyond the middle.of the valve; anterior furrow a little 
narrower, about midway between the posterior one and the anterior 
margin of the valve, nearly vertical in its upper half, bent obliquely 
backward below and joining the posterior furrow. Posterior lobe 
occupying nearly one-half of the valve; median lobe subglobose, en- 
tirely isolated; anterior lobe small and low. ‘The antero-ventral pro- 
