310 CABBONIFKKOUS FORMATIONS AND FAUNAS OF COLORADO. 



CONOCAKDIUM Biumi, 1835. 



CONOCARDIUM .sp. 



One (specimen of Conocardiuin has come to hand, but it is too poor for identifi- 

 cation. It is one of the forms with an elongated posterior portion like 0. catanto- 

 mnm, but it is fully three or four times larger than that species. It is so far known 

 only in the Leadville region. 



Locality and horizon. — Leadville district (station 23Y5); Leadville limestone. 



GASTEROPODA. 



PLATYCERAS Conrad, 1840. 



Keyes, following European usage, advocates" the employment for this group of 

 Paleozoic shells of the name given by Montfort to a closely similar type of living- 

 ones. He states,* "the two genera last mentioned [Capulus and Platyceras] are prac- 

 tically coextensive, and, since the first has precedence of more than thirty years, it 

 should be used instead of the second." It is admitted on all hands that the recent 

 Ga/puli are closely related to the Platycerata., but it seems to me impi-obable that the 

 same type has survived without change in its generic characters from middle or pos- 

 sibly early Paleozoic to recent time. The circumstance that the Gapuli are fairly 

 abundant at the present day, and that the Platycei'ata enjoyed their maximum 

 development during the middle Paleozoic, declining rapidty in the Mississippian,'^ and 

 being comparativelj^ rare during most of the Carboniferous and Mesozoic, at least 

 lends color to this view. I therefore propose to retain the Paleozoic Cajndi under a 

 name distinct from their living representatives. Regarding the eligibility of the 

 name Platyceras, Keyes further states: '^ "Even if the group to which Conrad gave the 

 name Platyceras were a valid one, it is very questionable whether the term could 

 stand, inasmuch as it has been pre-occupied for three-quarters of a century. It has 

 long been known that Geoffrey in 1764 proposed for a genus of Coleoptera the name 

 Plal/yceras, a term which was later emploj^ed bj'' Latreille, and which continues to 

 the present day in good usage as originally proposed." I find, however, that the 

 spelling given hj both Bronn '' and Scudder'' for the Coleopterous genus is not Platy- 

 ceras, as Keyes cites it, but Platycerus. The objection to the employment of Conrad's 

 Platyce7'as being thus removed, I shall retain it in the force and significance in which 

 it has long been known. 



aMissouri Geol. Surv., vol. 5, 1894, p. 164 et seq., and in rf Ibid., p. 164. 



other publications. e Index PalEeontologicus, pt. 1, Stuttgart, 1848, p. 992. 



iilbid. /U. S. Nat. Museum, Bull. 19, 18S2, p. 251. 

 clbid., p. 172. 



