INVERTEBRATES. 119 



AVICTJLOPECTEN coLLETTi. AVorthen. 



PI. XXII, Figs. 13 and 8b. 



Arii-iii<jpecten coUetti, Worthen. March, 1884. Bulletin No. 2, of the Illinois State Museum 

 of Natural History, page 22. 



Shell below the medium size, inequilateral, ovate. Left valve 

 slightly convex, ears well defined and unequal in size. Anterior 

 ear small, triangular, posterior ear rather larger than the 

 anterior, ornamented with four or five longitudinal costse and 

 fine transverse lines of growth, with a well defined notch at its 

 junction with the lateral border. Lateral borders straight nearly 

 to the middle of the valve and thence rounding into the ventral 

 border. 



Surface of the valve ornamented with 35 to 40 slightly convex 

 radiating cost* which increase in size towards the free borders 

 of the shell. 



Right valve nearly flat, ears rather more prominent than on 

 the opposite valve, and radiating costae less distinct. Length 

 from the beak to the ventral margin % inch; greatest breadth 

 11 1(i inch; length of hinge line, % inch. 



.Vanied in honor of Prof. John Collett, the able State Geolo- 

 gist of Indiana. 



Position and locality : From the shaly beds of the Keokuk 

 group, fYawfordsville, Indiana. 



Collector, Frank H. Bradley. 



No. 2512 of the Illinois State Museum. 



A VICULOPECTEN EDWARDSi. Worthen. 



PI. XXII, Fig. 2. 



Aviculopecten edwardsi, Worthen, March, 1884. Bulletin No. 2, of the Illinois State 

 Museum of Natural History, page 22. 



Shell of medium size, obliquely ovate, right valve very convex, 

 breadth a little more than the length ; anterior ear rather large, 

 triangular, posterior oar not preserved ; posterior border oblique, 

 and extending in a nearly straight line from the beak to the 

 basal margin; anterior border moderately rounded from the ear 

 to the basal margin. 



Surface of the valve ornamented with ten or twelve rather 

 sharp prominent costce,"with two or three indistinct ones in the 

 intervening spaces on the lower portion of the shell. 



