Rathbun.] 20 [May 16, 



with which are given the number of raised lines that mark the sur- 

 face near the margin: (1) lengtli 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 4.6 

 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 dejiecta 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. Hail 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 Msec uni, 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 Mfecuru and Curua. (Geol. Comm. 1876.) Erere. (?) (Mor- 

 gan Ex., 1871.) 

 Chonetes Onettiana Rathbun. 



Bull. Buff. Soc. Nat. Sci. i, no. 4, p. 253, pi. x., 1874, 



Rare in the Devonian sandstone of Ererd. (Morgan Exs., 1870 and 

 '71; Geol. Comm., 1876.) 

 Chonetes Herbert-Smithii Hartt, MS. 



Rathbun, Bull. Buft. Soc. Nat. Sci., i, no. 4, p. 251, pi. x, 1874. 



An examination of the manj' specimens of Chonetes obtained at 

 Erere in 1876, proves a greater variation to exist among the forms 

 referred to this species than was previously indicated, and it is prob- 



