104 PALAEONTOLOGY OF ILLINOIS. 



GENUS BHYNCHONELLA. Fischer. 

 RHYNCHONELLA ILLINOIENSIS. Worthen. 



PI. XI. Figs. 3-3a,3b,3c. 



Rhynchonella illinoiensis, Worthen, March, 1884. Bulletin No. 2 of the Illinois State 

 Museum of Natural History, page 21. 



Shell of about medium size, transversely ovate to sub-circular, 

 wider than long, front nearly straight in the middle, beaks ob- 

 tusely pointed. Ventral valve t-lightly elevated near the beak, 

 and depressed towards the front into a broad, shallow nx'shil 

 sinus, which is occupied by about eight sub-angular plications 

 that interlock in front with those of the opposite valve. There 

 are also from eight to ten similar plications on each side of the 

 sinus. 



Dorsal valve sharply depressed at the sides, nearly flat from 

 the beak to the front, which is elevated into a broad mesial 

 fold on which there are about eight elevated plications that in- 

 terlock with those of the opposite valve, and about the same 

 number on each side of the mesial fold. Length of an average 

 size specimen 6 / 1H inch; width % inch; thickness in front about 

 equal to the length. The small individuals of this species, if 

 found in Upper Silurian strata, might be mistaken for R. wil- 

 soni. 



Position and locality: Coal Measures, Peoria county, 111. 



Collector, Mr. Giffprd and W. H. Adams. 



No. 2537 of the Illinois State Museum. 



GENUS LINGULA. 

 LINGULA VARSOVIENSIS. Worthen. 



PL XI, Fig. 8. 



Liugula carsovieusis, Worthen, March, 1884. Bulletin No. 2 of the Illinois State Mus- 

 eum of Natural History, page 24. 



Shell of medium size, longitudinally oblong, more than one- 

 third longer than wide, with sub-parallel sides, the broadest 

 part being a little below the middle of the shell. 



Basal margin broadly rounded, beak rather prominent, an- 

 terior margin more narrowly rounded than the basal, but not 

 quite perfect in the specimen in hand. 



