36 CAKBONIFEKOl'S AMMONOIDS OF AMP:RICA. 



auxiliary series of lobes outside of the umbilicus. In this family Waagen 

 groups the following subfamilies: 1, Medlieottinte; 2, Beloceratiute ; 3, 

 Beueckeina?; 4, Hedenstroemiua? ; all of which have representatives in 

 American Paleozoic or Triassic strata. 



It is not likely that Prodromites is a descendant of Beloceras, since the 

 septation is quite different in the two genera; and unless Hedenstroemia 

 should be found to have a keel, it is not j^robable that it has descended 

 from Prodromites. Beloceras is commonly- placed in the family Prolecani- 

 tidse, although it antedates any tjqjical species of Prolecaniies. On the 

 other hand, Medlicottia, which appears to be closely related to Prodromites, 

 seems certainly to have been a descendant of the typical Prolecantidse. 

 No solution of these questions is possible until the ontogeny of several of 

 these genera is known, which is prevented, at present, by a scarcity of 

 specimens. Until other evidence is forthcoming Prodromites is placed 

 under the Beloceratidne, as an ancestral group of the family Pinacoceratida;. 



The genus is not founded solely on Miller's figure, which is not accu- 

 rate, nor even on his type specimens, but also on three other specimens of 

 this species and one of another species, bringing out certain characters that 

 did not show on Miller's tjqje. The writer has had at his disposal for study 

 four specimens of Prodromites gorhyi Miller, and one of P. pramaturus 

 Smith and Weller, all of which, except one, belong to the paleontologic 

 collection of the Walker Museum, University of Chicago, to the authorities 

 of which the writer's thanks are due for the use of the specimens. The 

 first specimen, No. 6208," is Miller's type of Goniatites gorhyi, and came 

 from the Chouteau limestone. Pin Hook Bridge, Pettis County, Mo. A 

 second specimen, No. 6474, was obtained from Prof Gr. C. Broadhead; it is 

 better preserved than the type, but is in the same sort of limestone, and 

 while it is merely labeled "Chouteau limestone, Pettis County, Mo.," it 

 probably came from the same locality as the type. A third specimen. No. 

 6722, is recorded merely from the Kinderhook stage of Burlington, Iowa. 

 The material in whic^h it is preserved is a buft' 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 magnesiau bed, which lies immediately below the Burlington limestone, 



« The numbers refer to the AValker Museum collection. 



