OF THE FAMILY OF KAIADES. 453 



green, finely wrinkled, obscurely radiated and glabrous ; marks 

 of growth very perceptible; cardinal tooth of right valve 

 crest-like, recurved, and clasping the side of the opposite one ; 

 lateral teeth lamelliform and curved ; anterior cicatrices dis- 

 tinct; posterior cicatrices confluent; dorsal cicatrices form a 

 line across the cavity of the beaks, and are very perceptible ; 

 cavity of the beaks very wide and shallow; nacre pearly, 

 bluish-white, violet-purple and iridescent. 



Remai'ks. — Mr Barnes noticed this as a connate shell. His 

 description of the cardinal tooth does not agree with my spe- 

 cimens, except in the younger ones, in which this tooth is 

 more lamellar. Tlie recurved tooth hooking or clasping the 

 other, when the valves are closed, is very remarkable. 



In some specimens the lateral and cardinal teeth form an 

 uninterrupted curve line, when the cardinal tooth is quite 

 lamelliform ; in others the latter is small and lobed, age pro- 

 ducing much effect on it in this respect. 



7. Sy3iphynota Tenuissima. Plate XI. fig. 21. 



Testa angusto-elliptica, inaquilaterali, transversim rugosa, compressa ; 

 valvulis tenuissimis fragillimisque ; margine dorsali connata ; dente 

 cardinali prominentia exigiia, laterali unico et acicula^'i in valvuld utrd- 

 que ; natibus depressis ; ligamento celato ; margaritd cceruleo-albd et 

 purpurea, iridescente. 



Sliell narrow-elliptical, inequilateral, transversely wrinkled, com- 

 pressed ; valves very thin and very fragile ; dorsal margin connate; car- 

 dinal tooth a small lobe ; lateral tooth acicular and single in both valves; 

 beaks depressed ; ligament concealed; nacre bluish-white and purple, 

 iridescent. 



Hab. Ohio. T. G. Lea. 



My Cabinet. 



Cabinet of T. G. Lea. 



Cabinet of Prof. Vanuxem. 



Cabinet of P. H. Nicklin. 



