772 Report or THE StatE GEOLOGIST. 
In the brachial valve a median septum is more or less strongly 
developed and divides a simple ovate adductor impression. The 
hinge-plate is short and deeply divided by a median groove. 
The brachial supports consist of spiral cones with their bases in 
apposition and parallel to the axial plane of the shell, and 
their apices directed toward the lateral margins. The jugum 
has been shown by Guass to have the following structure: The 
lateral branches approach and unite near the middle of the 
interior cavity, forming a very short stem, from the posterior 
extremity of which is given off a pair of arms. These curve 
JO 
Fie. 307.—The spirals and jugum of Merista herculea, Barrande. (Davipson, from a 
preparation by Guass.) 
downward to the primary lamellze of the coil and returning 
meet the lateral branches below their point of union, the whole 
forming a scissors-shaped arrangement essentially like that of 
MeristetxA, differing only in minor respects indicated under the 
discussion of that genus. 
External surface of the valves smooth or with concentric 
growth-lines. Shell-substance fibrous. 
Type, Merista herculea, Barrande. Etage E. 
Distribution. Upper Silurian.—Devonian. 
Dicamara, Hall. 1893. 
(Plate 33, figs. 16-19.) 
Meristoid shells with a “shoe-lifter” in each valve; that of 
the brachial valve being divided by a vertical median septum, 
Type, Dicamara plebeia, Sowerby (sp.). 
Distribution. Devonian. or 
