BRracHIoPoDA. 803 
have been extended to the surface of the internal ridge on the 
pedicle-valve. 
In front of the base of the jugum the primary lamelle become 
at once narrow and delicate, and it not infrequently happens, in 
——_—_———_. 
¢ 
Fia. 374.— The brachidium of Celospira concava, Hall. 
Fia. 375.— Profile, showing the elevation of the jugum. The stem of the jugum is probably 
broken and, therefore, shorter than is natural. 
Zo 
preparations of the interior, that the more fragile portions of the 
ribbon are lost, leaving only the umbonal blades and the jugum. 
(Type, Celospira concava, Hall. Upper Silurian (Clinton 
group) — Middle Devonian.) 
Subgenus Leptoccelia, Hall. 1859. 
(Plate 39, figs. 18-27.) 
Shells similar to Ca osprra in general contour, structure of 
hinge, cardinal process, muscular scars and internal septa, 
though of larger size and coarser plication. In the original 
diagnosis of Lerrocasrta the shell was described and figured as 
possessing a terebratuloid loop. It was, however, distinctly 
stated that the evidence of this structure was confined to a 
single specimen containing cavities in its filling of quartz, which 
corresponded to the restoration given. Subsequent investigations 
have not corroborated this observation. 
Specimens are not often favorably preserved for the retention 
of the brachial apparatus, those from Cumberland, Maryland, 
being replaced by silica and often filled with coarsely crystallized 
quartz, while those from New York, Gaspé and South American 
localities are usually in the form of casts in an arenaceous sedi- 
55 
