PRONORITES. 41 



The only species witli Avliich Tnxl romites prmmaturus n\\^\\t be com- 

 pared is P. r/orhifi, from the same horizon, but in P.prrematanis the abdomen 

 is sHo-htly broader, tlie shell ratlier thicker, the septa rather more complex, 

 and the umbilicus slightly wider than on P. f/orhi/i at the same diameter. 

 In the figures and descriptions of the septa a diftei'ence between the two 

 species may easily be seen. 



Ilimi'iixions. 



Millimeters. 



Diameter fi2 



Height of last wliorl .'U 



Height of last whorl from the iireceding 21 



Width of last whorl 9.5 



Involution 13 



Width of umbilicus 6. 5 



This specimen was septate throughout, and when complete must have 

 been much larger. 



Occurrence. — Only a single specimen is known. No. 6223 of the 

 paleontologic collection. Walker Museum, University of Chicago, from the 

 Lower Carboniferous, Kinderhook limestone, goniatite beds of Rockford, 

 Ind., near the base of the ]\Iississippian series. 



Family PRONORITID^. 



As it is now generallv admitted that Pronorites and its allies can not be 

 classed under the family Prolecanitidi^ in the strictest sense, some new 

 designation for this group ought to be given. E. Hang" proposed the name 

 Ibergiceratidse for this phylum, but the genus on which the family was 

 founded, Ibergiceras, has since been shown to be merely an immature form 

 of Pronorites cyclolohm. Since Pronorites is the principal genus of this 

 group, and is the ancestor of a large number of genera that occur in the 

 Permian and Trias, the writer proposes to call the family Pronoritida^, 

 including Pronorites, Slcanites, Projyinacoceras, and Medlicottia. These all 

 seem to have been derived from Paraprolecanites, which may tlieu Ije 

 considered as the family radicle.' F. Freeh'' has used the term Pronoritiuse 

 for this group, regarding it as a subfamily. 



Genus Pronorites Mojsisovics. 



In the adult stage Pronorites is discoidal, has high, narrow whorl, with 

 nearly parallel sides, is very involute, and has narrow umbilicus. 



The siphonal lobe is three-pointed, the first lateral lobe divided into 



"Etudes sur les t ioniatites, p. .50. ''Die Dyas, p. 481. 



