Bnich'iopo'la of the Cindnnati Group, 9 



Genu.s Lhujula — (Bruguiere, 1792). 



[Etym. — Lingula, a little tongue.) 



Subequivalvo, equilateral, longitudinally ovate or subpentagonal, 

 both valves channeled equally at the beaks, for the passage of the 

 pedicle (one beak a little longer and more pointed than the other, 

 which latter has a narrow, internal, flat area) ; internally, each valve 

 has a thickened pad in the middle, and the shorter one has in front of 

 it a prominent internal septum. 



The species of this genus grow wider proportionally with age. 



Lingula quadrata — (Eichwald, 1829). 



Subequivalve, equilateral, broadly oval, depressed convex; sides 

 nearly straight and parallel, or slightly curved; extremities nearly 

 equal in width, the first broadly rounded, cardinal extremity slightly 

 narrower and somewhat angularly sloped ; beak marginal, not promi- 

 nent; exterior surface of the shell marked by strong concentric stria?, 

 and along the middle by distinct longitudinal striae, which are equally 

 visible when the outer shell is exfoliated. A longitudinal depressed 

 line marks the shell from the beak nearly half way to the base. 



It is disthiguished by its very large size and subelliptical form. It 

 varies in length from one inch to an inch and a half, and in width 

 from three fourths of an inch to an inch. 



Its range is co-extensive with the Cincinnati Group, but good speci- 

 mens are extremely rare. 



Lingula Fan Hornei—(S. A. Miller) 



Fig. ]. — Lin/ulu Van II(jinei. 



General form acute, elongate ovate ; beak of dor.sal valve projecting 

 beyond the beak of the other valve; valves about equally convex 

 along the middle and compressed toward the front ; surface marked 

 with concentric lines. 



Length of specimen, 0.75 inch; greatest width, 0.47 inch; convexity, 



0.18 inch. 



