Rathbun.] 20 [May 15, 
with which are given the number of raised lines that mark the sur- 
face near the margin: (1) length 11 mm., breadth 13 mm., height 
2.25 mm., raised lines thirty (absent from cardinal angles); (2) length 
11.5 mm., width 14 mm., height 4 mm., raised lines forty; (3) length 
13 mm., width 18 mm., height 3.5 mm., raised lines thirty-two (want- 
ing on cardinal angles); (4) length 20 mm., width 29 mm., height 4:5 
mm., raised lines forty-eight. 
In this species we have included a number of forms, which might 
have served for the formation of several species were not the mate- 
rial in our possession so abundant as to afford a complete series of vari- 
ations, uniting the different forms closely together. The younger 
shells are proportionately the narrower, and in after growth they in- 
crease more rapidly in width than in length. The younger forms 
are also frequently more convex in proportion to their size, than are 
the older, which often become broadly flattened or depressed along 
the middle. The older and broader forms are the more abundant 
ones. ‘The smaller varieties of this species, having the length and 
breadth about equal, appear to represent Chonetes deflecta Hall, of 
the Hamilton group of New York State; the larger, more transverse 
forms, however, more closely resemble, at least in shape, some of the 
large species of Chonetes described by Prof. Hall from the Upper 
Helderberg group of New York. The nearest related one seems to 
be C. acutiradiata Hall. 
This species of Chonetes is exceedingly abundant in the Devonian 
sandstone of the Rio Mecurt, and the collection brought from there is 
very large, representing many varieties. A few specimens were also 
found on the Rio Curua. The single ventral valve of a Chonetes de- 
scribed, but not named, in the Bull. Buff. Soc. Nat. Sci., Jan. ’74, p. 
253, very probably belongs to this species. 
Rios Mecurt and Curud. (Geol. Comm. 1876.) Ereré. (?) (Mor- 
gan Ex., 1871.) 
Chonetes Onettiana Rathbun. 
Bull. Buff. Soc. Nat. Sci. 1, no. 4, p. 253, pl. x., 1874. 
Rare in the Devonian sandstone of Ereré. (Morgan Exs., 1870 and 
71; Geol. Comm., 1876.) 
Chonetes Herbert-Smithii Hartt, MS. 
Rathbun, Bull. Buff. Soc. Nat. Sci., 1, no. 4, p. 251, pl. x, 1874. 
An examination of the many specimens of Chonetes obtained at 
Ereré in 1876, proves a greater variation to exist among the forms 
referred to this species than was previously indicated, and it is prob- 
