41 



M. DECUSSATA. Mont. Sup. p. 20. F. p. 463. 

 Ovate, waved at the margin, white with irregular con- 

 centric ridges decussated by regular concentric striae ; 

 umbo obtuse recurved and not central ; a broad erect 

 tooth in one valve, in the other a projecting plate with a 

 small indenture for the reception of the tooth of the 

 opposite valve, i. Rare. 



GENUS. ANATINA. 



Transverse, subequivalve, gaping at both valves or in 

 one only ; no cardinal teeth, one broad primary 

 tooth in both valves projecting interiorly : a lateral 

 plate running obliquely under the primary teeth. 



* Teeth transversely fixed. 



A. CONVEXA. Turton. B. p. 44. t: 4. /. 1, 2. 

 MYA. C. Wood. G. C. p, 92. t. 18. /. l.Turt. C. 

 D.p. 100. AMPHIDESMA C. F. p. 431. MYA. 

 DECLIVIS. Don. t. 82. Oval-oblong, angular and 

 slightly truncated anteriorly, rounded posteriorly, very 

 convex, light and brittle, rusty white, with irregular 

 concentric striae ; beaks close and and subcentral ; teeth 

 narrow and very central. l....2i. Paignton. 



A. PUBESCENS. Turt. B. p. 45. t. 4./. 3. AMPHI- 

 DESMA. P. F. p. 431. -MYA. P. Mont. p. 40. 

 Turt. C. D.p. 99. /. 35. M. DECLIVIVIS. Lin. T. 



