TRIBE MYTILACEA. 249 
M, Uncuraris. Lam. 23.—E. t. 216. f. 3?—Semiovate, ante- 
riorly dilated, rather thin, angulated and compressed ; posterior 
edge nearly straight but slightly bulging out towards the ventral ; 
epidermis blackish with a larger or smaller portion tinged with ful- 
vous; beaks small. 3. Indiaand New Holland. The specimen in 
the museum at Paris has the hinge margin short and straghtish. In 
all probability the next species. (judging from the original specimens) 
is no more than a depressed variety of this shell. 
M.Pranutatus. Lam. 24. Ovate rhombic, rather depressed, 
m part blue, part white, at the beaks acute; angle of the anterior 
side, central. 3. Nen Holland. 
M. Borrauts. Lam. 25—M. Envuuss. Gould.Mas. f. 82. Oblong, 
thick, rather tumid, bluish or purplish white, under a black epider- 
mis; hinge margin rather long, forming an arch but never a distinct 
angle with the anterior ventral margin: posterior margin nearly 
straight, neither incurved nor flattened: beaks not approximate, 
inclining inwards, divergent: interior dark blue, white towards the 
obtuse beaks, hinge witha few denticles. Newfoundland, N. Ame- 
rica. 13..34. Allied closely to Edulis, but I think distinguishable 
by the above characters. In adult typical specimens of our common 
mussel, the anterior margin is subparallel to the posterior ; m Borealis. 
the shell being dilated anteriorly, this is by no means the case. It 
ts likenise broader, with the surface less compressed both anteri- 
orly, and posteriorly. The anterior ventral margin is well arcuated. 
M. Ancustanus. Lam.26. Narrow-oblong, subarcuated, ob- 
tusely angulated, bluish, the beaks inflected. 13. “Shape of 
Edulis without its posterior swell: two small teeth.” 
M. Corneus. Lam.27. Oblong, thin, yellowish horn-colonr, 
obscurely rayed, anteriorly curved ; posterior side straight: with 
a brown spot. 13. 
M. Gattorprovinciatis. Lam. 28.—Phil, p. 72. t. 5. f. 12, 13. 
Ovate-triangular, bluish-black, anteriorly much compressed, the 
striz of growth strong and the epidermis usually glossy : dorsal 
margin straight and rather long, forming an obtuse but distinct 
angle with the anterior ventral, and thence sweeping in an uninter- 
rupted curve to the ventral edge: posterior side depressed, white 
but of a yellowish brown when covered by its epidermis, edge 
nearly straight, very slightly incurved: much attenuated towards 
the acute beaks: hinge with a fewdenticles. Mediterranean. 23. 
Variable in its breadth but easily to be distinguished from the next by 
its longer dorsal margin and distinct angle. The umbonal ridge is 
more acute.' 

1 The Ditaratus of Gray. (W.S. t. 2. f-2.) seems allied to this 
species. 
