TRIBE MYTILACEA. 201 



pearly, a flat plate at the beaks uniting the sides of the shell. 1 j- 

 N. Europe, lakes and rivers. l 



M. Strigatus 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 

 in each valve. If. This beautiful shell varies peculiarly in its 

 outline but may be easily recognized by its brilliantly coloured cuticle 

 and the rich nacre of its in tenor. Were it not for its teeth, it might 

 easily be confounded with the Modiolce, as in some of its varieties, the 

 posterior extremity projects beyond its beaks, and the dorsal and ven- 

 tral edges are almost subparallel. 2 



PINNA. 



Longitudinal, wedge-shaped, equivalve, gaping at the broader end, and 

 pointed at the apex, with the beaks straight and acute ; hinge lateral 

 and without teeth ; ligament marginal, linear, very long and some- 

 what internal. 



P. Rudis Lin. 1159.— J), p. 324.— Lam. l.—Ch.f. 773.— E.t. 

 199./. 3.— List. t. 373. f. 2l±.—Seba. 3. t. 92. upper figs.— W. t. 

 12./. 1. Large, elongated oblong, orange rufous, with but a few 

 large elevated radiating sulci which are armed with a 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. — Atlantic and American 

 Seas. 3 



1 Add likewise the Dreissena Afrtcana Vanbeneden. in An. de 

 Sc. 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, f. — Senegal. 



See too the D. Cyanea, Vanbeneden. An. Sc. Nat. 



2 To this section, belong likewise the M. Vulgaris. Chem.f. 732. 

 (copied E. t. 218./. 4. and W. t. 12./ 15.— D. p. 307.) the M. 

 Leucophceatus Say. Jour.Philad. 6. t. 11./ 15. p. 263. — andM. 

 M. Dilatatus TV. S. t. 2./ 2. 



3 M. Deshayes refers to this species, as a variety, the Flabellum 

 of Lamarck 2.— (Kn. 2. t. 26. / 2.— Ch. / 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. 



