BRAcHIOPODA. 869 
as a very broad, continuous lamella, which is not reflexed though 
somewhat curved upward on the anterior margin. From the 
inner margins of this lamella, on its exterior and lateral 
Fie, 510. Fie. 511, Fie. 512, 
c Stringocephalus Burtini, Defrance. 
Fia. 510. Umbonal cavity of the pedic!e-valve with discrete deltidial plates. 
Fie 511. The internal sheath or projection of ths pedicle-passage. 
Fie 512.. The umbona! cavity of a pedicle-valve in which coalescence of the deltidial plates 
is almost complete. (QUENSTEDT.) 
extension, arises a series of linear processes converging toward, 
and some of them perhaps reaching the crura. A low, thick 
median septum extends for about half the length of the valve. 
Fic. 518. Stringocephalus Burtini, Defrance. 
A restoration of the interior, show!ng the internal pedicle-sheath and the strong median sep - 
tum of the pedic e-valve; the great cardinal process, one of its terminal lobes (c) Jying on 
either side of the septum; the furm of the loop with the radial filaments extending from the 
anterior lamellae (d) tothe crura. At (qa) is the insertion of the diductor muscle, (6) that of 
the adductor. (HoERNEs.) 
The muscular impressions on both valves are exceedingly 
obscure, and have never been fully described or illustrated. 
Surface smooth, with fine concentric growth-lines; sometimes 
a low median sinus exists on both valves near the margin. 
121 
