28 Colorado College Studies. 



Measurements. — ^Tlie shell of this auunoiiite attains a 

 heif^ht of at least 125 mm.; that of the body-chamber about 

 half as much. 



Occurrence (ind History. — In Texas this is the common- 

 est Sphenodiscus of the Comanche Peak limestone; and in 

 Kansas it is, so far as the writer has observed, the only rep- 

 resentative of its genus in the Champion shell-bed and the 

 Kiowa shales, being associated there with the common Fred- 

 ericksburg and Kiowa ammonite, Scliloenbacliia perui'iand, 

 Von Buch. All of the truncate Sphenodisci hitherto found 

 either in the Comanche Peak limestone and Ciiampion shell- 

 bed, or in later rocks of the Comanche series, are here pro- 

 visionally included under this species, though some of the 

 supposed varieties may prove to be distinct, and some are 

 doubtless of stratigraphic importance. 



Messrs. Stanton and Hill have recently* called attention to 

 the fact that a Sphenodiscus differing from S. pedernalis. 

 Von Buch, by its truncate venter, occurs in the Belvidere 

 beds of Southern Kansas.f I had observed the same fact in 

 1889, as witnessed by figures 1, 2 of Plate I, here reproduced 

 from rough lead-pencil sketches which I made at that time, 

 of a Champion shell-bed specimen that I was once inclined 

 to separate from S. pedernalis and describe as new. I after- 

 ward gained the impression that the truncate character of 

 the periphery was inconstant, and did not signify a species 

 distinct from S. pedernalis, but only a variety. Hence the 

 broad use that I have generally made of the name Sphenod- 

 iscus pedernalis. 



I now agree fully with the above-cited statement of Messrs. 

 Stanton and Hill, and confirm also my own former supposi- 

 tion of the distinctness of these truncate Sphenodisci from 

 S. p)edernalis. 



The specific name, belviderei (afterward changed to bel- 

 viderensis), was first applied to this species in 1890 in my 

 article "On the Cheyenne Sandstone and the Neocomian 

 Shales of Kansas" + where I listed '' Ammonites Belviderei''^ as 



♦Except the two flRunis noted as sketchod in 1«S9, tlio manuscript and drawings 

 of tlie present article were prepareil in tlie spring of 1*97. 

 + Am. Jour. Sci., Tliird Series, Vol. L, June, 1895. 

 % Bui. Washburn Coll. Lab. Nat. Hist., No. 11, March, 1S9U. 



