BRACHIOPODA — TELOTREMATA. 343 



386. A. umbonata (Conrad). (Fig 438, c-d.) Devonic. 

 Differs from A. prceumbona in its smaller size, distinct though 



narrow mesial sinus and proportionally longer hinge line which 

 here usually forms the greatest width of the shell. 



Marcellus-Chemung of New York, Pennsylvania, Kentucky, 

 Indiana. 



387. A. nana Grabau. (Fig. 439.) Devonic. 

 Small, transverse. Brachial valve convex, bearing a shallow 



mesial depression. Surface covered with numerous elongated pits. 

 Marcellus and Hamilton of New York. 



Fig. 439. Amboccelia nana. (After Fig. 440. Amboceelia planoconvexa X 

 Grabau), enlarged, X 2 - 2 (Ind.Geol. Survey.) 



388. A. planoconvexa (Shumard). (Fig. 440.) Carbonic. 

 Breadth and length about equal. Brachial valve circular except 



for its truncation by the hinge line and nearly flat, with minute 

 beak and narrow cardinal area. Pedicle valve convex ; mesial 

 sinus represented by a slight flattening in front. Surface seen to 

 be finely granulose under a lens. 



Widely distributed throughout North America. Conemaugh of 

 Pennsylvania, Ohio and West Virginia. 



CVIII. Metaplasia Hall and Clarke. 

 Spiriferoid but differing from Spirifer in the reversal of sinus and 

 fold, i. e. y the pedicle valve bears the median fold and the brachial 

 the median sinus. The teeth are supported by lamellae, the mus- 

 cular impressions of the pedicle valve are separated by a short, 

 thick septum and the cardinal process is strong and bilobed. De- 

 vonic. 



389. M. pyxidata Hall. Devonic. 

 Small. Pedicle valve with a strong, broad elevation, furrowed 



by a narrow sinus down the middle. Brachial valve flat and 

 marked by a broad depression in the center of which is a narrow 

 elevation. Surface when perfectly preserved both concentrically 

 and longitudinally striated. 



Oriskany of New York, Maryland, Ontario. 



