INVERTEBRATES. 



319 



LAM ELLI BRANCH I AT A, 



GENUS CELENOMYA, Meek. 



CILENOMYA MARIA, Worthen. 



a Side view. I) Dorsal view, nat, size. 

 <:iinn<>inu<i Maria, WOETHEN, February, 1882. 

 Bulletin No. 1, of the Illinois State Museum of Natural History, p. 39. 



Shell elongate, sub-cylin- 

 drical, anterior side much 

 compressed and aperture en- 

 tirely closed; posterior side 

 truncated and widely gaping. 

 Base slightly convex in out- 

 line, rounding up gradually 

 in front and abruptly be- 

 hind, dorsal side a little 

 concave from the beaks 

 to the posterior extremity. 

 Beaks depressed, incurved, 

 and located about one- 

 fifth the entire length of the shell from the anterior side. 



Two conspicuous furrows commence at the beak, the anterior one 

 crossing the valve obliquely to the base of the shell at a point about 

 two-fifths of its entire length from the anterior side ; the posterior 

 one crossing the shell much more obliquely, and terminating at the 

 base of the shell, near its posterior extremity. 



