4] 
M. Decussata. Mont. Sup. p. 20,—F. p. 463.— 
Ovate, waved at the margin, white with irregular con- 
centric ridges decussated by regular concentric striz ; 
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. +. Rare, 
Grnus.—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. fi 1, 2.— 
Mya. C. Wood. G. C. p, 92. t. 18. f. 1.—Turt. C. 
D. p. 100.—Ampuiprsma C. F. p. 431.—Mya. 
Deciivis. Don. ¢. 82.—Oval-oblong, angular and 
slightly truncated anteriorly, rounded posteriorly, very 
convex, light and brittle, rusty white, with irregular 
concentric striz ; beaks close and and subcentral ; teeth 
narrow and very central. 14....23. Paignton. 
A. Pupescens. Turt. B. p. 45. t. 4. f. 3.—Ampui- 
DESMA. P. F. p. 431.--Mya. P. Mont. p: 40.— 
Turt. C. D. p. 99. f. 35.—M. Decuiivivis. Lin. T. 
