1878.] Ney (Rathbun. 
broader than in the Ereré forms; but there seem to be no other 
differences of importance. 
This species is the most abundant one in the Devonian sandstone 
of Ereré. It is nearly equally common in the sandstone of the Rio 
Mecurt, but only a few very small specimens were brought from the 
Curudé. (Morgan Exs., 1870 and ’71; Geol. Comm., 1876.) 
Strophodonta perplana Hall. 
Strophomena perplana Conr., Jour. Acad. Nat. Sci., vii, p. 257, 
1842. Strophomena pluristriata Conr., idem., p. 259. Strophomena 
delthyris Conr., idem., p. 258. Strophomena crenistria Hall, Rept. 
Fourth Geol. Dist. N. Y., p. 171, 1843. Strophomena (Strophodon- 
ta) fragilis Hall, Tenth Rept. State Cab. N. Y., p. 143, 1857. 
Strophodonta fragilis Hall, Rept. Geol. Survey of Iowa, p. 496, 1858. 
Strophodonta perplana Hall, Paleont. New York, Iv, pp. 92 and 
98, 1868. 
This common species of the Devonian of New York State, ranging 
there through the Upper Helderberg, Hamilton and Chemung 
groups, occurs very abundantly in the Devonian sandstones of the 
Rios Meeurti and Curua, and in these localities undergoes many of 
the variations peculiar to it in N. Y. It sometimes attains a very 
large size. ( Geol. Comm., 1876.) 
Spirifera duodenaria (?) Hall. 
Delthyris duedenaria Hall, Geol. Rept. 4th Dist. N. Y., p. 171, 
1843. Spirifer duodenaria Hall, Twelfth Rept. State Cab. N. Y., 
p- 88, 1859. Spirifera duodenaria Billings, Canadian Jour., p. 256, 
1861; Geology of Canada, p. 372, 1863; Hall, Paleont. N. Y., rv, p. 
189, 1868. 
The commonest species of Spirifera at the Rio Mecuru locality is 
one which belongs very near to- Spirifera duodenaria, if it is not 
identical with it. The Brazilian variety is sometimes more trans- 
verse than S. duodenaria, of New York. The plications of the shell 
are generally of the same size, but are sometimes smaller. The 
ventral sinus is of more uniform size in the Brazilian, than in the 
American variety, and seldom becomes as broad at the front. The 
cardinal extremities are never much flattened in the dorsal valve, 
and never at all in the ventral, though this. portion of the valve is 
almost always smooth. The depressions intervening between the 
plications are generally narrower than the plications themselves, 
and are regularly rounded. ‘The hinge-area is narrow as in S. duo- 
