BRACHIOPODA. 
303 
The pedicle-valve is regularly convex, becoming slightly concave on the 
cardinal slopes. It bears a moderately broad cardinal area, coextensive with 
the hinge-line, which is divided by a broad, open delthyrium, which, in no 
observed condition of growth, bears a covering of any sort, but is filled 
by the cardinal process of the other valve. The base of the delthyrial 
cavity is thickened and transversely striated, probably by the attachment 
of the pedicle-muscle. The teeth are not situated at the extremities of 
the delthyrial margins, but lie within and in front of them, arise from 
the bottom of the valve as two erect, divergent subquadrate crests, rest¬ 
ing upon low ridges which bound the muscular area. These peculiar teeth 
are smooth and abrupt on their inner faces, while their outer faces are 
deeply crenulated. A low groove separates each from the cardinal area. 
The muscular area is broadly flabellate, extending more than half-way across 
the valve, and consists of two large diductor scars enclosing a narrow median 
pair of adductors. 
The brachial valve is slightly concave, often nearly flat. Cardinal area nar¬ 
row, but clearly developed; chilidium prominent. Cardinal process large, erect, 
smooth on its posterior surface, and bilobed at its summit. Each of these lobes 
is excavated above, so that the upper portion of the posterior wall is free from 
the rest of the process. In front of this is a broad, smooth floor, sloping 
toward the bottom of the valve. The margins of this area form the elevated 
socket-walls, and their anterior extremities are the bases of the crura. The 
dental sockets are deep and their outer walls corrugated for the reception of 
the teeth. The posterior portion of the sockets and the lower part of the 
cardinal process are covered by the erect, convex chilidium. At the anterior 
edge of the cardinal process lies a broad, thick, not elevated median ridge, 
which gradually narrows and becomes developed into a sharp, thin septum, 
attaining its highest point at about the center of the valve, whence it slopes 
rather more abruptly downward, terminating at the anterior third of the valve. 
From the crural bases extends a pair of long, slender lamellar processes, which 
curve outward, are directed upward, again converge and unite with the median 
septum on its lateral faces and just in front of its highest point. Slightly con- 
