BRACHIOPODA. 313 



Genus CHONETELLA, Waagen. 1884. 



18S4. Chonetella, Waagen. Mem. Geol. Survey of India ; Palseontologia Indica, Series xiii, vol. i, 



No. 4, p. 657, pi. Ixxxi, tig-s. 3-8. 



Diagnosis. Shell small, normally concavo-convex. Surface rounded, with 

 radial striae; cardinal area narrow; deltidium, cardinal spines and teeth as in 

 Chonetes. In the pedicle-valve the adductor impressions are elongate, and are 

 partially enclosed by the larger cardinals. The brachial valve has a small 

 trilobed cardinal process, which is continued into a low median septum. The 

 muscular area is quadripartite and very distinct. The 

 brachial ridges are sharply defined and appear to origi- 

 nate near the outer extremities of the posterior adduc- 

 tors, making a broad outward, and a more abrupt inward 

 curve completing one volution. Surface in the pallial 

 region strongly papillose. j.,^ „g cuoneteiia n.mua. 



Tj^e, Chonetella nasuta, Waagen. Upper Carboniferous. After waagen. 



Observations. Dr. Waagen has proposed this division for a single species 

 from the Productus limestone of India. Aside from the broadly curved brachial 

 ridges, its characters are so strongly chonetoid as to render its separation from 

 Chonetes exceedingly difficult.* The author surmises that some small shells 

 figured by DavidsonI and regarded by him as varieties of Productus longispinus, 

 from the Carboniferous shales of Lanarkshire, Scotland, belong to the same 

 group. 



* The trilobed cardinal process is described in its anterior aspect only, and it is quite probable that upon 

 its posterior face it would be found moi'e similar to that of Chonetes. The crural plates are very obscure, 

 making- the process ajipear fi'ee and erect ; but this is also true of some species of Chonetes, e.g., Chonetes 

 coronata. Conrad. 



t Carboniferous Brachiopoda, jil. xxxv, figs. IS, 19. 



