BRACHIOPODA. 65 



the beaks of both valves, produces a " shouldered " appearance. There is a low- 

 sinus on the pedicle-valve which is apparent only over the pallial region ; this 

 is accompanied by a sliglit fold on the opposite valve. The apex of the pedicle- 

 valve is closely incurved, concealing both deltidiuni and foramen. On the 

 interior the teeth are moderately prominent and are supported by strong dental 

 plates, which not only extend to the bottom of the valve, but are continued 

 forward for about one-third the length of the shell, and inclose a narrow, 

 elongate muscular area.* In the brachial valve the hinge-plate appears to be 

 short and constructed on the same plan as that of Meristina and Whitfield- 

 ELLA, with two diverging crural bases divided by a median groove, or a sub- 

 triangular pit, and is supported by a median septum extending for about one- 

 half the length of the valve. The spirals have their apices directed laterally 

 and consist of nine or ten volutions of the ribbon. External surface smooth. 

 Shell-structure fibrous, impunctate. 



The external expression of the shells of Hindella is rendered peculiar by 

 the fulness and close incurvation of the beaks, and these are distinguishing 

 features. While the character of the loop is unique, the deep muscular scar 

 of the pedicle-valve, the structure of the hinge-plate, and the smooth external 

 surface, are features which demonstrate the close relationship of the genus to 

 Meristina and Whitfieldella. 



Genus MERISTINA, Hall. 1867. 



PLATE XLVII. 



1828. Atrypa, Dalman. Kongl. Veteiiskaps Akail. Handling-., p. 134, pL v, fig. 3. 



1860. Athyris, Roemer. Die Silurische Fauna der westlichen Tennessee, p. 70, pL v, fig. 12. 



18fi3. MeriMella, Hall. Transactions of the Albany Institute, vol. iv, ]>. 212. 



1866. Meristella, Davidson. British Silui-ian Braohiopoda, p. 109, pi. xi, figs. 1-13. 



1867. MtT'isUna, Hall. Twentieth Rept. N. Y. State Cab. Nat. Hist., p. 157. 

 1867. Meristina, Hall. Palaeontology of N. Y., vol. iv, p. 299. 



1872. Meristella, Hall and Whitfield. Twenty-fourth Rept. N. Y. State Cab. Nat. Hi.'it., p. 196. 

 1875. Meyistina, Hall and Whitfield. Palseontology of Ohio, vol. ii, p. 132, pi. vii, figs. 5, 6. 

 1878. Meristella, Etheridge. Quarterly Journal Geological Society London, p. 597. 



* All the internal characters of the valves here described have been derived fi-om transveree sections of 

 the fhell. The material examined, most of which lias been placed at our service by the kindness of its col- 

 lector, Pi-ol'e.=sor Alpheus Hyatt, has aftbided no interiors or single v.alves. The figures given above, of 

 sections across the umboiial region, show some of the features mentioned. 



