Raymond : Rkalhioi'oua and Osiracoda ok the Cha/v. 23.'> 



C'.enus Rakinesquina Hall and Clarke. 

 15. Rafinesquina champlainensis Ra\ nioiul. 



KiifuifSiiuiiui cliamp!iii>unsis Kav.monu, igoj. Bulltlin AincTiLaii I'lik'oiUology, 



W.l. HI. p. 373. PI. 18. figs. 5. 6. 



This large Rafinesquina is very abundant in the middle layers of 

 the Chazy, and occupies the same place in the fauna of the Chazy 

 that K. (iltcniata does in the Trenton. In general form it resembles 

 R. (iltcniala, but is much more near!\- hemispheric. 



6 7 



Fig. 6. Rafinesquina champlainensis Raynioncl. A pedicle valve. Natura 

 size. 



Fig. 7. The same species. A specimen showing the Lracliial valve, the cardiiia 

 area, and the deltidium. Natural size. 



Fig. 8. The same species. Outline profile of a specimen cut along the median 

 line, showing the curvature of both valves. 



Description. 

 Shell large, ventricose, almost hemispheric. Length and width 

 nearly equal. Hinge line usually a little 

 longer than the width below, and the 

 cardinal extremities are produced into 

 broad rounded ears. The pedicle valve 

 is strongly and evcnh- convex, the highest 

 point being about the middle of the \alvc. 

 The brachial valve is flat on the umbo 

 and concave in front, following the cur- 

 vature of the opposite valve. Cardinal 

 area on the pedicle valve rather wide. 

 Delth\ rium covered by a broad con\ex 

 deltidium. Area of brachial valve linear. 

 The surface is marked by very numerous fine radiating stride, every 



Fig 9. Rafinesquina cham- 

 plainensis Raymond. The im- 

 pression of a brachial valve. 

 Natural size. 



