f 21+ ] 
GENUS XÎ. 
Mytilus. Muscle. 
bivalves with equal valves, and fhut clofc. 
The hinge is toothlefs, and conflits of a 
longitudinal and linear furrQW,»-»The 
animal^ an AJcidia Î 
GENRE XL. 
Mytilus. Moule. 
Bivalves à bat tans égaux, qui fe ferinent 
exaftement. La charnière ell fans dents^, 
& eompofée d’une rainure longitudi- 
nale & en ligne. — L’animal, eil un, 
AJcidia-? 
^ FLUVIATILES,. Riyer.. 
XLVI. 
M. Cygneus. Great Horse Muscle. 
* FLUVI ATÎLES.. 
XLVL 
JlVÂ Y ^ I LU S fiuviatilis maximns,. admodim fenuis exfujca viridejcens, Cygneu-r. 
Mufculus lattis rnaximus, tejia admodum tenui,. ex fujco viridejcens,. ■palujiris. Lilr. Appv 
H. An. Angl. p. 8. tir. 30. tab. fig-3- & App. H. An. Angl. in Goedart. p. 
tit. 3<D. tab; I. fig. j. — Mujculus latus- maxinius tenuijfimus- é’ cœ.rtileo- viridejcens, Jere: 
falujiris. H.. Conch, tab. 156. fig. r.i. 
Mytilus jluminum maximns Jubviridis. Piott Oxfordfh. cH. 7. §' 3-2. — M. Cygneus. S-wam. 
Fenn. Brit. Zool. No. 78. tab; 67. fig. 78. and in- many oj our Englijh writers this and the' 
following kind are indijcrhninately put together. 
Mujculus flnviaiilis' maximus, prof unde ftriatus, iatut y tejïa admodum tenui, ex fujco virt-^ 
dejcens, interdum riifejcens, intus argenteus. Gualt. I. Conch, cab. 7. fig. F.. 
Concha tejia obl'onga ov at a longitudinaliter fubrugofa, poftice. comprejfo.-promîniüa. Lin. F., 
Suecv I. p. 380. No. 1332.: — Cygneus. Mytilus tejia emta. antice comprejfiujcula fragilijima. 
Une ejpece large,, de cincq a. 
fix pouces en largeur, ou de coté à coté„ 
& feulement environ deux pouces & demi 
à trois pouces en longueur, ou dès lacharniere 
au bord oppofé i d’une forme ovale j mince, 
demitranfparente, fragile, & îegere j & 
les valves font fort profondes ou concaves* 
Uexterieur, â rides norabreufes, fortes, 
îranfverfalcs de concentriques, & porte 
fouvent 
cardine. laîerali. S. N.. p..i 158.. No; 257.. 
This is 3 large and broad Jpecies, from 
five to fix inches broad, 01 from fide to fide, 
and only about two- inches and a half to 
three inches long, or from the hinge to the 
oppofite or bottom margin -, of an oval 
Jbape-, thin, femitranfparent, brittle, and 
lip:ht 5 and the valves are very deep or 
concave. 
Outfide, wrought with numerous ftrong 
concentric tranfverfe wrinkles, and has 
often 
