310 MOLLUSCOIDEA—BRACHIOPODA SUB-KINGDOM V 
Oehlertella, Hall and Clarke (Lingulodiscina, Whitfield). Much like Schizo- 
crania, but the ventral valve has concentric growth lines, and no radiating 
striae. Ventral pedicle area greatly elevated and transected by a narrow 
open fissure. Devonian to Lower Carboniferous ; North America. 
Schizobolus, Ulrich. Devonian; North America. (7?) Monobolina, Salter. 
Family 2. Discinidae. Gray. 
Derived Discinacea with an open pedicle notch, in early life, in the posterior 
margin of the ventral valve, which is closed posteriorly during neanic ee. leaving 
a more or less long, narrow slit, partially closed by the listrium. Ordovician to 
Recent. 
Orbiculoidea, VOrbigny (Fig. 512). Shells inequivalved, sub-circular, or sub- 
elliptical in outline. Apices eccentric. Ventral valve depressed, convex, or 
flattened. Dorsal valve larger, usually de- 
pressed, conical. Pedicle furrow originat- 
ing behind the apex, extending over a 
greater or lesser portion of the radius of 
the valve, and produced at the distal end 
into a short tubular sipho, emerging on the 
interior surface near the posterior margin. 
Surface with fine, crowded or distant, 
rarely lamellose, concentric lines occasion- 
Fig. 512. ally crossed by radiating lines. Ordovician 
ee, Cdn Utuan Gals Uh (otter 2 bone notaceous > Nonthrand South America, 
i ea anes: nope ond grisly alee 
Wee Were ct bay a a es Discina, Lamarck. Very much lke 
Orbiculoidea, but the pedicle emerges through the ventral shell antero- 
posteriorly, immediately beneath the beak, instead of through a sipho postero- 
anteriorly as in that genus. Recent. 
Until recently, Discina embraced all fossil Discinoid shells, but at present 
this genus seems to be restricted toa single species, 
D. striata, living off Cape Palmas, West Africa. 
Discinisca, Dall (Fig. 513). Like Orbiculoidea, 
but’ with a small septum, as in Discina, behind 
which is an impressed area, externally concave and 
internally elevated. This is perforated by a longi- 
tudinal fissure, extending from a short distance — pjseinisca tamellosa, Brod. Recent: 
behind the septum nearly to the posterior margin. Pero, aes Le area by 
Tertiary to Recent ; North America and Europe. 
Schizotreta, Kutorga. Ordovician and Silurian; Russia and North 
America. 
Lindstroemella and Roemerella, Hall and Clarke, are genera related to Orbi- 
culoidea. Devonian; North America. 

A 

Fic. 513. 
Superfamily 3. CRANIACEA. Waagen. 
Cemented calcareous Neotremata without pedicle or anal openings at maturity. 
Ordovician to Recent. 
