BRACHIOPODA. 
223 
the inner surface of the valve (P. latiplicata, P. multiplicata). This feature seems 
to some extent subject to variation within specific limits; that is, being more 
or less of an individual peculiarity. 
The brachial valve of P. latiplicata and P. mvltiplicata shows four distinct 
ovate muscular scars about the anterior prolongation of the median septum, 
and these are of quite the same character as those in the corresponding valve 
of Anastrophia. Indeed, in all of these species the interior structure does not 
materially differ from that of Anastrophia, though, being a thin-shelled group, 
the muscular impressions are not as clearly developed. In exterior characters, 
however, the differences are more significant. 
To the six American species which are above referred to Parastrophia, are 
probably to be added the Rhynchonella Scotica, Davidson, from the Llandeilo of 
Ayrshire,"*" and the Pentamerus (Airypa) rotundatus, Sowerby, from the Wenlock 
of Wenlock Edge.f 
It is probable that upon a shell of similar structure to Parastrophia, Gagel 
has recently based his proposed genus Branconia, P. bnrussica, from the Lower 
Silurian diluvial boulders in Ostpreussen (Die Brachiopoden der cambrischen 
und silurischen Geschiebe im Diluvium der Provinzen Ost- and Westpreussen : 
Beitrage zur Naturkunde Preussens herausgegeben von der Physikalisch- 
Oekonomischen Gesellschaft zu Konigsberg, p. 62, pi. iv, fig. 12. 1890). From 
the description and figures of the exterior of a single specimen it appears to 
be a trihedral shell of rhynchonelloid aspect, but with a median septum in each 
valve. What the inner relations of these septa were, or any other interior 
characters of the shell, is not made known. It seems very doubtful if the 
author is correct in regarding the more convex valve as the ventral, and the 
shallow valve as the dorsal, but it will be impossible to pass judgment on the 
value of the genus as now defined. So early a representative of this structure 
should receive further elucidation. 
* Davidson, Silurian Brachiopoda, Suppl. p. 201, pi. xi, figs. 26 a-d. 
t Silurian Brachiopoda, p. 150, pi. xv, figs. 9-12 
