PLATE LXXI. 



(Figures 1-3 copies ; 4, 5, 24-33 by K F. Whitfield ; (!-10, U-16, 34-38 by G. B. Simpson ; 11-13, 17-23 by E. Emmons). 



Genus BARRANDELLA, gen. nov. 



Page 241. 



Barrandella linguifera, Sowerby. 



Figs. 1, 2. Doi-sal and profile views of a normal individual ; showing- the chara*;ter of the exterior and 



the well defined median fold on the brachial valve. 

 Pig. 3. A longitudinal median section of the valves ; showing the .small spondylium and extremely short 

 median septum of the pedicle-valve, and one of the septal plates of the brachial valve. 

 Wenlock limestone. Dudley, England. 



(Figures 1-3 after Davidson ) 



Bakrandella ventricosa, Hall. 



Figs. 4, 5. Front and doi-sal views of a typical example ; showing the fold upon the brachial valve, its 

 faint plication, and the cavities of the median septa. 

 Niagara dolomites. Waukesha, Wiscmisin. 

 Pigs. 6, 7. Ventral and profile views of a ventricose specimen with a low sinus on the pedicle-valve. 

 Pigs. 8-10. Dorsal, profile and front views of a smaller individual having the fold and sinus distinctly • 

 plicate. 



Niagara dolomites. Near Milwaukee, WiscoTisin. 



Barrandella fornicata, Hall. 



Figs. 11-13. Profile, doi-sal and ventral views of the exterior of a specimen of average size ; showing the 

 median fol<l on the brachial vahe, the single broad plication in the sinus of the pedicle-valve, 

 and the fainter plication of the lateral slopes. 

 Clinton group. Lockjxyrt, Neio York. 



Barrandella Areyi, sp. nov. 



Figs. 14-16. Dorsal, profile and ventral views of a normal example ; showing the strongly plicated fold 

 and sinus on the brachial and pedicle valves i-espectively, and the sharp plication of the lateral 

 slopes. X 2. 



Clinton group. Rochester, New York. 



Barrandella Barrandii, Billings. 



Figs. 17, 18. Don<al and ventral views of a large and typically developed individual ; showing the broad 

 plication in the median sinus of the pedicle-valve and the corresponding median groove on the 

 opposite valve ; also the finer plication of the inedio-lateral region. 

 Figs. 19, 20. Dorsal and profile views of a smaller and more gibbous specimen. 



This species, in its earliei' growth stages, is very similar in form and contour to £ fornicata 

 (figs. 11-13), but the rapid increase in size of the median xilication in the sinus of the pedicle- 

 valve, during the later growth stages of the shell, has the eft'ect of revei-sing the relative 

 position of fold and sinus in the final condition of gi-owth. 

 Anticosti group. Bescie River, Anticosti. 



