TRIBE MYTILACEA. 2511 
pearly, a flat plate at the beaks uniting the sides of the shell. 11 
N. Europe, lakes and rivers. ' 
M. Srriecatus Hinds Z, P. 1844. Shape varying from subo- 
vate-oblong to elongated oblong, smooth, rather solid, cuticle thick, 
of a yellowish green, with broad darker green wavy stripes anteriorly: 
dorsal angle indistinct, posterior ventral edge not much compressed, 
beaks scarcely terminal : inside purple, nacreous : two small teeth 
ineach valve. 19. This beautiful shell varies peculiarly in its 
outline but may be easily recognized by its brilliantly coloured cuticle 
and the rich nacre of its interior. Were it not for its teeth, it might 
easily be confounded with the Modiole, as in some of its varieties, the 
posterior extremity projects beyond its beaks, and the dorsal and ven- 
tral edges are almost subparallel.? 
PINNA. 
Longitudinal, wedge-shaped, equivalve, gaping at the broader end, and 
pointed at the apex, nith the beaks straight and acute ; hinge lateral 
and without teeth ; ligament marginal, linear, very long and some- 
what internal. 
P. Rupts Ldn. 1159.—D. p. 324.—Lam. 1.—Ch.f. 773.—E. t. 
199. f. 3.—Iast. t. 373. f. 214.—Seba. 3. t. 92. upper figs.—W. t. 
12.f.1. Large, elongated oblong, orange rufous, with but a few 
large elevated radiating sulci which are armed witha few extremely 
large and rather distant semitubular spines ; dorsal edge the longer 
and nearly straight, the base (or anterior edge) rounded and run- 
ning obliquely to the ventral margin. 18.—A¢lantic and American 
Seas.® 

1 Add likewisethe DrrtssenA Arricana Vanbeneden. in An. de 
Se, Nat.1835. Triangular-oblong, slightly but regularly foliaceous, 
with two radiating crest like keels diverging from the rounded beaks: 
ventral edge without a notch for the byssus: within of a somewhat 
dull bluish white. 2.— Senegal. 
See toothe D. Cyanra, Vanbeneden. An. Sc. Nat. 
2 To this section, belong likewise the M. Vutearts. Chem. f. 732. 
(copied E. t, 218. f. 4. and W. t. 12. f. 15.—D. p. 307.) the M. 
Leucopnaatus Say. Jour.Philad. 6. t. 11. f. 15. p. 263.—and M. 
M. Dinaratus WoOSot52: f. 2. 
3M. Deshayes refers to this species, as a variety, the Franen.tum 
of Lamarch 2.—( Kn, 2. t. 26. f. 2.—Ch. f. 769. Reddish rust 
color, pellucid, subtruncated and rather broad at the anterior mar- 
gin; the longitudinal sulci straight and armed with small or moderate 
sized whitish scales. Shorter and smaller than Rudis. 

