44 
IIOSTIU'M, Ll'NULK, KTC., IN BIVALVES. 
stiuHed the Naiads, thinks the development of tlie rostniin is 
induced by agitated or running waters, but tliis is evidently not 
Ful. 107. — A Rosirate or Ileaked llnalve. 
Anoiionta cygnva \‘:\.Xy^diniinuta Clessin, left valve, 
Canal, Louth, Lincolnshire, collected hy Mr. H. Wallis Kew, F.L.S. 
r. the produced posterior end or rostrum. 
the only predisposing cause, as the shell now figured was taken 
from the sluggish waters of the Louth canal, Lincolnshire. 
The Lunule is the oval or heart-shaped depressed space in front 
of, or anterior to, the nmbones, and opposite to.the ligament, and is 
sometimes defined by a more or less noticeable line. In the separated 
valves this space has been termed the Anterior Sinus, and 
necessarily exists on both valves. 
The Escutcheon or Corselet is the corresponding depressed space 
sometimes e.xistingon the 
posterior dorsal or liga- 
mental margin. In the 
separated valves it appears 
as an elongate space on 
each side of the ligament, 
and has been called the 
Posterior Sinus. 
iMocpiin Tandon, the accomplished and accurate French con- 
chologist, and many French and German authors, erroneously regard 
the lunule as the space posterior to the umbones, and the corselet 
or escutcheon as that anterior to them, a view diametrically opposed 
to that adopted by English and American authors. Draparnaud, who 
instituted the terms, clearly defines the position of the two areas, and 
establishes the accuracy of the English opinion upon this point. 
Fkl 108 . — Anodonta nnatinn v. coniftlanaia Rossm., 
( Jumfrieston, near Tenby, 
Collected by Mr. Fred. Walker. 
Showing tlie position and aspect of the Lunule 
and Ibscutcheon. In. lunule ; c. escutcheon. 
