BRACHIOPODA. 57 



In the brachial valve the cardinal process is quite prominently developed 

 and is distinctly bilobed. The socket walls are elevated and recurved ; ante- 

 riorly they are produced into sliort crural bases which are not free, but rest 

 upon the bottom of the valve. The muscular area is narrow and elongate, and 

 consists of a pair of central adductor scars embraced posteriorly by a broader 

 pair. From the anterior margin of this area arise two vascular trunks which 

 diverge outwardly and recurve, following the margins of the valve. These give 

 off a series of branches externally and probably a shorter series toward the 

 center of the valve. The ovarian markings are very distinct about the bases 

 of the dental sockets. 



The external surface of tlie shell is smooth or covered with very fine con- 

 centric lines. The shell substance is fibrous and apparently impunctate. 



Whether this species was spiriferous has not been determined, none of the 

 specimens examined having shown evidence of brachial supports. In some 

 respects the characters of the species are suggestive of Orthis ; for example, 

 the well developed, bilobed, recurved cardinal process, filling the delthyrium 

 of the brachial valve and extending beyond the plane of the cardinal area; 

 the vascular sinuses, and to some extent, the arrangement of the muscular 

 impressions. These features, taken in connection with the delthyrium of the 

 pedicle-valve, which does not appear to have been covered, though sometimes 

 partially filled with an apical accretion, may perhaps be interpreted as confirm- 

 atory evidence of the non-spiriferous character of the species. 



Metaplasia pyxidata was described from the Oriskany fauna of Cumberland, 

 Maryland. It is known to occur also in the Oriskany of New York and Canada, 

 as well as in the decomposed chert of the Corniferous limestone in the Province 

 of Ontario. 



It may be here observed that the very peculiar species Spirifer cheiroptijx, 

 described by d'Archiac and de Verneuil,* from the middle Devonian at Paflfrath, 

 and its ally in the Carboniferous limestones of Vis.-, N Oceani, d'Orbigny,t have 



*0n the Fossils of the Older Deposits of the Rhenish Provinces: Trans. Geol. Soc. London, vol. vi, 

 p. 370, pi. XXXV, figs. 6, a, b, 1842. 



t Prodrome de Pal^ontologie stratigrapbique, pi. i, p. 149, 1850. See, also, Db Koninck, Faune du Cal- 

 caire earbonifSre de la Belgique, 6e partie; Brachiopodes, p. 132, pi. xxviii, figs. 11-16, 1887. 



