PRODROMITES, A NEW AMMONITE GENUS 259 



Museum at the University of Chicago, to the authorities of which the writers' 

 thanks are due for the use of the specimens. The first specimen, 1 No. 6208, 

 is Miller's type of Goniatites gorbyi, and came from the Chouteau limestone 

 at Pin Hook Bridge, Pettis county, Missouri. A second specimen, No. 6474, 

 was secured from Professor G. C. Broadhead. It is better preserved than the 

 type, but in the same sort of limestone, and while it is merely labeled "Chou- 

 teau limestone, Pettis county, Missouri," it probably came from the same 

 locality as the type. A third specimen, No. 6222, is recorded merely from 

 the Kinderhook beds of Burlington, Iowa. The material in which it is pre- 

 served is a buff or yellowish, rather finely crystalline limestone, the position 

 of which in the Kinderhook section at Burlington is probably near the top, 

 between the oolitic limestone and the buff magnesian bed, which lies imme- 

 diately below the Burlington limestone of Osage age, or in the basal portion 

 of the oolite bed. This horizon may then be correlated with the Chouteau 

 limestone of central Missouri. 



A fourth specimen of P. gorbyi was studied by the writers in the collection 

 of Fred. Braun, of Brooklyn, N. Y. It came from the Kinderhook goniatite 

 bed of Rockford, Indiana, associated with Prolecanites lyoni Meek and 

 Worthen, Aganides rotatorius de Koninck, Muensteroceras owc?ii Hall, M. 

 fiarallelum Hall, and thus is certainly in the zone of Aganides rotatorius of 

 the Tournaisian horizon of the Lower Carboniferous. 



A fifth specimen of the genus, No. 6223, belongs to a new species (P. 

 praematurus Smith and Weller). It came from the Kinderhook goniatite 

 beds of Rockford, Indiana. 



Geologic horizon. — Since this genus occurs in the same horizon, in rocks 

 of different lithologic character, and in three localities separated by hundreds 

 of miles, it may be considered as characteristic of the Chouteau limestone 

 horizon of the Lower Carboniferous, equivalent to the lower part of the Tour- 

 naisian horizon of the European Dinantian formation. At present Prodromites 

 is unknown outside of America, and but two species are known, in the Mis- 

 sissippi valley region, from the three localities mentioned. 



Prodromites gorbyi Miller. Plate VI, Figs. 1. Plate VII, Fig. 9. 

 Plate VIII, Figs. 1, 2. 



1 89 1 Goniatites gorbyi Miller, Adv. Sheets, Seventeenth Rep. 

 Geol. Survey of Indiana, p. 90. Plate XV, Fig. 1. 



1892 Goniatites gorbyi Miller, Seventeenth Rep. Geol. Survey 

 of Indiana, p. 700. Plate XV, Fig. I. 



Neither the description nor the figure given by Miller of this type is accu- 

 rate, the drawings of the septa being entirely too generalized. 



'The numbers refer to the Walker Museum collection. 



