762 Rerort or THE State GEOLOGIST. 
Metaplasia, Hall. 1893. 
(Plate 31, figs. 21-24.) 
Shells spiriferoid in exterior, with the relative convexity of the 
valves reversed, the pedicle-valve bearing a median fold and the 
brachial valve a broad median sinus. 
The teeth are stout and unsupported by lamellz; the posterior 
extremities of the diductor impressions in the pedicle-valve are 
deeply impressed and separated by a short, thick septum. 
Anteriorly the muscular area is less clearly defined; from its 
distal margin diverge two ridges which were probably of vascular 
origin, and a few radiating furrows of similar character are 
seen on the lateral portions of the valve. 
In the brachial valve the cardinal process is quite prominently 
developed and is distinctly bilobed. The socket walls are 
elevated and recurved ; anteriorly they are produced into short ~ 
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. Brachial supports unknown. 
The external surface of the shell is smooth or covered with 
very fine concentric lines. The shell substance is fibrous and 
apparently impunctate. 
Type, Metaplasia pyxidata, Hall (sp.). Oriskany sandstone. 
But a single species is known. 
Verneuilia, Hall. 1893. 
(Plate 31, figs. 18-20.) 
Shells spiriferoid with a deep median sinus on each valve. 
The exterior of the valves is divided by two strong divergent 
ridges into three depressed areas. 
Type, Verneuilia chiroptyx, d@Archiac and de Verneuil (sp.) 
Middle Devonian. 
Distribution. Devonian — Carboniferous. 
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