CEPHALOPODA. 455 



This species has the form and proportions of G. discoideus and G. uniangularis ; 

 but is readily distinguished by its open umbilicus, and by the shallow umbilical 

 lobe, the high lateral saddle, acute ventro-lateral lobe, and short dorsal lobe. 



It differs from all the other forms known to me, in the disposition and 

 character of the septa, and the proportions of the umbilicus. In the latter 

 feature, and in its septal arrangement, it is somewhat nearly related to G. lamel- 

 losus of Sandberger (Verstein. des Rheinischen Schichtensystems in Nassau, tab. 8, 

 fig. 1), but is a much less rotund form, with the lateral laces more gently curved 

 and the periphery narrower. The species is of rare occurrence, and little is 

 known of its vertical and horizontal distribution. 



Formation and locality. In the Chemung group, near Ithaca, N. Y. 



GONIATITES COMPLANATUS. 



1'I.ATE I.XX, FI(iS. 8-11. 



Clymeniaf complanata, Hall. Geolog. Surv. of N. Y. : Rep. Fourth Dist., pp. 243, 244, fig-. 5. 1843. 

  'tmjilanata, " Descriptions of New Species of Fossils, etc., p. 35. 1881. 

 " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 63. 1862. 

 Chjmenia Erato, Hall. Descriptions of New Species of fossils, etc., p. 36. 1S61 



Fifteenth Rep. N. Y. State Cab. Nat. Hist,, p. 64, pi. 10, fig-. 1. 1862. 

 Ooniatites complanatvs, Hall. Description! of New Species of Goniatidae, p. 1. May, 1874. 



Twenty-seventh Rep. N. Y. State Mus. Nat. Hist., p. 132. 1875. 

 Clymeiiia Erato, Hall. Illustrations of Devonian Fossils: Cephalopoda, pi, 70, fig's. 6, 7. 1876. 

 Goniat'iteg {Clymeniaf) complanatus, Hall. Illustrations of Devonian Fossils: Cephalopoda, pi. 70. 1876. 



Shell discoid ; inferring from the depth of the umbilicus, the disc may have 

 had a thickness of about eight mm., where the diameter has been about 

 thirty-five mm. 



Volutions about four or more, gradually expanding from the apex, the 

 outer ones embracing the inner for about one-fourth to one-third of their 

 width, or sometimes a greater proportion. In their natural condition they 

 are rounded and subventricose, but are usually flattened. Umbilicus wide, 

 exposing all the inner volutions. Transverse section short, semi-elliptical, or 

 trapezoidal, with the apex rounded, and the base indented by the preceding 

 volution, the baso-lateral angles auriculate. The enlargement of the volutions 

 is very gradual to the termination of the septate portion, where the rate 

 of increase is moderately augmented. 



