KEPORT OF THE STATE GEOLOGIST. 



547 



In the brachial valve the beak is scarcely prominent, and the 

 muscular markings are essentially as in the opposite valve, but 

 more sharply developed. Beneath the beak is a faint mnbonal 

 scar, the lines diverging from which are discernible. The long 

 compound lateral curves have a considerably greater degree of 

 curvature than in the pedicle-valve, their posterior portion inclos- 

 ing a thickened area, which is continued into a peculiar low and 

 thickened median septum, bifurcating in the middle of the valve, 

 the angle being occupied by an intercalated ridge, which extends 

 for twice the length of the branches of the septum. The central 



Fig*. 234, 235.— Lingulct Criei. Internal cast and interior Fig. 236. — Lingula 



of posterior portion of pedicle-valve. (Davidson.) Criei. Internal 



cast of pedicle- 

 valve. Natural 

 size. (Davidson.) 



scars are situated further backward at the junction of the median 

 septum with the posterior thickened area. 



Type, Barroisella sulspatulata, Meek and Worthen (sp.). 

 Genesee slate (Devonian). 



Distribution. Silurian — Devonian. 



Subgenus Tomasina, Hall. 1S92. 



Externally like Lixgula. The pedicle-valve is very slightly 

 convex, its posterior margin being notched. This notch is 

 divided medially by a small triangular elevation at the base of 

 which, on the inner margin of the valve, are two conspicuous 

 articulating ( ( ) processes. 



Type, Tomasina Criei, Davidson (sp.). Silurian. 



Lingulepis, Hall. 1863. 

 (Plate 1, figs. 16, 17.) 

 Shells linguloid ; pedicle-valve attenuate and produced at the 

 beak; brachial valve obtusely ovate. 



On the interior the pedicle- valve bears a single large scar, 

 occupying the entire umbonal region, wmich is produced anteriorly 



99 



