252 Lingual Dentition of Gaeotis. 



the sandstone and shale, which at the east separate it from 

 its limestone, that a delta was there forming and pushing out 

 to the west, so that on the east the conditions requisite for 

 the formation of coal would first exist. On the east side of 

 the basin we find nine to ten feet in the lower division of the 

 bed, while on the west side we find only five to six feet. 

 I am led, then, to the following conclusions : 



1. The Great Bituminous Trough, west of the Alleghanies, 

 does not owe its basin shape primarily to the Appalachian 

 Revolution. 



2. The coal measures of this basin were not united to 

 those of Indiana and Illinois at any time posterior to the 

 lower coal measure epoch, and probably were always distinct. 



3. The upper coal measures originally extended as far 

 west as the Muskingum River, in Ohio. 



4. Throughout the upper coal measure epoch the general 

 condition was one of subsidence interrupted by longer or 

 shorter intervals of repose'. During subsidence the Pitts- 

 burg marsh crept up the shore, and at each of the longer 

 intervals of repose pushed out seaward upon the advancing 

 land, thus giving rise to the successive coal-beds of the upper 

 coal measures. 



5. The Pittsburg marsh had its origin at the east. 



XXI. — On the Lingual Dentition of Goeotis. 

 bt thos. bland and w. g. binney. 



Read January 6, 1873. 



The genus Goeotis was described by Shuttle worth,* founded 

 on a curious mollusk from Porto Rico. The lingual denti- 

 tion was said to be nearly the same as in Vitrina and Zonites, 

 the teeth arranged in oblique rows, centrals obtusely tri- 



*" Lamina lingiialis fere ut in Vitrina at Zonites constituta videtnr, papilla nempe 

 numerosaa in seriebiis utrinque obliqiiis orclinatre sunt : papilla centrali obtuse tri ' 

 dentata; raediis vix a centrali diversis; lateralibus autem subulnto-productis, arouatia 

 basi? bifurcatis. An maxilla adsit hteret." " E formatione liugfuse animal videtur 

 sine dubio carnivorum." Shuttlewortli, Bern Mit. 1S54, p. 34, 



