322 MOLLUSCOIDEA—BRACHIOPODA 7 SUB-KINGDOM V 
smooth shells, or sometimes with a few broad and obscure radiating undula- 
tions. Silurian; distribution probably general. 
Capellinia, Hall and Clarke. Like Pentamerus, but with the relative con- 
vexity of the valves reversed. North America. 
Clorinda, Barrande (barrandella, Hall and Clarke). Small galeatiform 
A B ( D 

Fic. 540. 
Conchidium biloculare, Linn. Silurian; Gottland. A, Shell of the natural size. B, Beak showing concave 
deltidium. C, D, Interior of dorsal and ventral valves, respectively (x7, Spondylium; S, Median septum of 
ventral valve, Fig. D; b, Dental lamellae ; c, Crura ; S, Septum-like supports, Fig. C). 
Pentameroids usually with smooth shells, rarely plicate. Spondylium with- 
out a supporting septum. Silurian; North America and Europe. 
Pentamerella, Hall. Much like Clorinda, but with strong plications and a 
narrow cardinal area. Devonian; North America. 
Gypilula, Hall (Sieberella, Oehlert), (Fig. 541). Galeatiform Pentameroids, 
with the median sinus on the dorsal, and the fold on the ventral valve. In 
D 

Fig. 541. 
_ A-C, Gypidula galeata, Dalm. sp. Devonian ; Gerolstein, Eifel. 4, Dorsal aspect, 1/;. B, Anterior aspect. 
C, Transverse section below the hinge-line. (Lettering the same as in Fig. 540 C, D.) D Conchidium Knightii, 
Sow. Silurian; England. 1/s. 
Sieberella there is no cardinal area, but in typical Gypidula there is a well- 
defined, cross-striated, cardinal area. Surface smooth or plicate. Silurian 
and Devonian ; North America and Europe. 
Amphigenia, Hall (Enantiosphen, Whidborne). Elongate - ovate, high- 
shouldered shells without median fold or sinus. Surface with concentric 
growth varices and faint radial striae. Dorsal valve with a large sub-quadrate 
hinge-plate perforated by the visceral foramen and without a cruralium. 
Middle Devonian ; North and South America, France, and Germany. 
Camarophoria, King (Fig. 542). Shells Rhynchonelliform with the surface 
