OF TUT. FAMILY <>r NAIADES. I '> ; 



green, finely wrinkled, obscurely radiated and glabrous; marks 

 of growth very perceptible; cardinal tooth of righi 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. 



Remarks. — Mr Barnes noticed this as a connate shell. His 

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

 cimen--, except in the younger ones, in which this t mth is 

 more lamellar. The 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 i< quite 

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

 ducing much effect on it in this respect. 



7. SVMFHYNOTA TENUISSIMA. Plate XT. fig. 21. 



Test" anguato-ellipticct, ineequilati rali, transverrim rugos 

 jlviilis tenuissimis fragiUimisqm ; margins dorsali connatd .• d 

 cardinali prominentia exigu i, laterali unico <l aciculari in valvu, 

 que; natibus depressis; ligamento celato; margarita caaruleo 

 purpurea, vridescente. 



Shell narrow-elliptical, inequilateral, transversely wrinkled, 

 pressed; valves very tbin and very fragile ; dorsal margin connal 

 dinal tooth a small lobe ; lateral tooth acicular and Bingle in both 

 beaks di at concealed; nacre bluish-white and pur] 



iridescent. 



Hah. Ohio. T. <;. Lea. 



My Cabinet. 



Cabinel of T. <i. I 

 Cabinel of Prof. \ anuxem. 

 Cabin( t of P. II. Nicklin. 



