106 
Arca R. Mont. p. 55. t. 27. f. 7.—Pen. 4. p. 217.— 
D. p. 245.—Oval, anteriorly produced, curved and 
rounded, glossy, pale horn color, with fine regular and 
reflected concentric striz, which however become ir- 
regular in crossing the very slight longitudinal anterior 
ribs; central tooth obsolete, margin entire. 4...4 
Frith of Forth. 
N. Minota. Turt. B. p. 178.—F. p. 402.—ARca. 
M. Pen. 4. p. 216.—Mont. p. 140.—Lin. T. 8. p. 92. 
—Dor. Cat. t. 1. f. 16.—D. p. 245.—Turt. D. p. 11. 
f. 38.—A. CaupaTa. Don. 3. é. 78.—Oval, anteriorly 
produced, curved and truncated, white or yellowish with 
a few ridges crossing the transverse striz, margin entire. 
3...4. Tenby, Sandwich, Scotland. 
OrverR.—MONOMYARIA. 
With one siphonal scar. 
TrinE.—MYTILACEA. 
Hinge with the ligament marginal, partly inclined, 
linear, extending along a great part of the anterior 
border. Rarely foliated and adherent. 
Grenus.—MODIOLA. 
Subtransverse, equivalve, regular, posteriorly very 
