BRACHIOPODA. 



65 



Figs. 25, 2G. 



Lingula Criei. Alter Davidson. 

 Internal cast and interior of posterior portion of 

 pedicle-valve. 

 Fig. 27. Inlcrnal cast of pedicle-valve. Natural size. 



Genus TOM A SIN A* gen. nov. 



Under the name, Lingula Criei, Mr. Davidson described, in 1881,f a linguloid 

 fossil from the Armorican grit of the Departement de la Sarthe, having a cardinal 

 area of such peculiar structure 

 as to render its separation from 

 the genus Lingula necessary. 



"The pedicle -valve is very 

 slightly convex, its posterior 

 margin being notched. This 

 notch is divided into two parts 

 by a small triangular elevation, 

 leaving on each side a well de- 

 fined depression or little cavity. Aside from this slight elevation, the valve 

 presents a gentle longitudinal convexity, which extends a little in front of the 

 center of the valve, the lateral portions of the shell remaining almost flat. The 

 opposite valve appears to have been somewhat more convex than that we have 

 described. 



" This notch in the area for the passage of the pedicle is very remarkable, 

 and I have never before observed it in any of the numerous species of the genus 

 which I have studied. In the interior of this same valve, beneath the pedicle- 

 aperture, there are two small processes with a depression between them, and 

 the central muscular impressions are well defined, but I have been unable to 

 find any other impressions upon the internal casts which M. Guillier 

 has sent me." 



The internal processes upon the cardinal margin are so large that they may 

 have served purposes of articulation to some extent. In this respect the fossil 

 shows structure similar to that seen in its associate in the same fauna, Lingula ? 

 Lesueuri, Rouault. 



* Out of regard for the memory of Mr. Davidson, to whom we are indebted foi- our knowledge of this 

 fossil, the above name is proposed. 



t Bulletin de la Societe Geologique de Fi'ance, p. 372. 1881 ; Note sur les Ling-ules du gi'^s armoricain 

 de la Sarthe, par M. A. Guillier, avec descriptions et figures des espfeces, par M. Th. Davidson, pi. vii. 



