PENNSYLVANIAN FOSSILS 



111 



Mes globus (some species of Chonetes of older publications) is 

 characterized by its double fold and sinus. It has some of the charac- 

 teristics of Chonetes including the spines on the hinge and the fine 

 radiating ornamentation. M. mesolobus (fig. 298) is the common species. 



Punctospirife r ( Spiriferina in older publications) is one of the many genera 

 of Paleozoic spiriferoid shells. It can be distinguished from the next genus by 

 the fact that there are no ridges on the sinus and fold. P. kentuckyensis (fig. 



299) is common. 



Fig. 299 



Fig. 300 



genus. H. mormoni (fig. 



Neospirifer ( Spirifer in older publications) is also a spiri- 

 feroid distinguished from Punctospirife r by the numerous ridges 

 on the sinus and fold. N. cameratus (fig. 300) is abundant. 



The next two genera are small shells and resemble Camaro - 

 toechia and Rhynchopora of the Mississippian. 

 Hustedia has strong radial ridges, extending from 

 beak to margin, which distinguish it from the next 

 301) is common. 



Wellerella ( Pugnax of older publications) resembles Hustedia but has ridges 

 only on the margin of the shell. A species of Wellerella (fig. 302) probably W. Fig. 301 



osagensis ( Pugnax utah of older publications) is common in some beds. 



Chonetes (fig. 303) is related to Mesolobus (see above) but has neither sinus 

 nor fold. Three species are common. 



Derby ia is a large, flat shell with numerous fine radiating 

 ridges, some of which are irregular and wavy. It resembles 

 Schuchertella and Schellwienella of the Mississippian (see fig. 

 250). Derby ia crassa (see fig. 252a) is the commonest of 3 species. 



The genus Rhipidomella , already noted for the Silurian, Devonian, and 

 Mississippian, is also present in the Pennsylvanian. It may be distinguished 

 from Derbyia by its more rounded outline, shorter hinge line, and larger 

 beaks which project distinctly over the hinge line. Rhipidomella pecosi (fig. 

 304) is common. 



Fig. 302 



Fig. 303 



Fig. 304 



The remaining genera of brachiopods are productids, a group which is particularly com- 

 mon from the Mississippian to the Permian. All of these genera are lumped together as Pro- 

 ductus in older publications. The genera can be identified from the key if well-preserved 



material is available; 

 otherwise, it is safer to 

 label shells of this group 

 "productids" and not to 

 attempt even generic 

 identification until better 

 material is at hand. 



Echinoconchus is 

 one of our largest pro- 

 ductids; the shell is 

 usually longer than wide. 

 Both valves bear spines 

 and the beaks are strong- 

 ly incurved. E. punc- 



tatus (fig. 305) is com- 



Fig.305 WBF ■ i 



mon in places. 



