JEFFERSON COUNTY. 



106. 



-f 



wm)& i 



395 



1. Pterinea undata. 



2. Nuculites inflata. 



3. Slrophomena alternata. 



4. Oibicula terminalis. 



5. Nuculilcs faba. 

 G. Atrj-pa rxtans. 



No. 1. Pterinea undata, is a rare species, found in the grey variety of tiie trcnton at 

 Watertown. 



No. 2. Nuculites inflata, is also a rare species, found at Watertown. The trenton is the 

 lowest rock in which the genus Pterinea has yet been discovered ; a fact wliicli is interesting, 

 inasmuch as this genus furnishes so many species in the rocks of the New- York System. 



No. 3. Stropliomena alternata, whose strife or markings are alternately fine and coarse. 

 This character is possessed, liowever, by other species, and hence is not in itself to be relied 

 upon as specific. 



No. 4. Orbicula terminalis, is a new species, in the grey trenton at Watertown. Both 

 valves are preserved in the specimen from which the drawing was made. It is rare ; only 

 one specimen has fallen under my notice. 



No. 5. Nuculites faha. This fossil is very abundant at Watertown, in the black irregular- 

 bedded limestone. 



No. 6. Atrypa extans, is found at Watertown in the grey limestone, and, at tiiis locality. 

 appears to be sufficiently common. I have not, however, seen it elsewhere. 



The Pterinea orbicularis (No. 3, Fig. 109), is found at Watertown, in the black limestone, 

 associated with Nuculites and Bellerophon profundus. Though quite common here, it is rare 

 to obtain it perfect, as the shell is thin. 



The corallines of the trenton limestone consist of several known genera, each comprising 

 but a few species. No. 3 (Fig. 99, p. 389), represents the Puffball favosite, which is pro- 

 bably as characteristic of this rock as any of which mention has been made. It is found at 

 Essex, Plattsburgh, Chazy, Watertown ; in fine, there is no locality of this rock which has 

 not furnished numerous specimens of this fossil. 



