94 
MOLLUSCA. 
Myt. edulis, L. This common Muscle is frequently seen s\is- 
jjended in extended clusters, along the whole coast of France, 
to rocks, piles, &c. &c. It forms a considerable item of food, 
but is dangerous if eaten to excess.* * * § 
Some of them are found fossilf . In the 
Modiolus, Lam. 
Separated from the Mytili by Lamarck, the summit is lower and 
near the third of the hinge. This summit is also more salient and 
rounded, approximating the Modioli more closely to the ordinary form 
of the bivalves;|;. We may also separate from the Mytili the 
Lithodomus, Cuv., 
In which the shell is oblong, and almost equally rounded at the two 
ends, the summit being close to the anterior extremity. The species 
of this subgenus at first simply attach themselves to stones like 
the common Mytili ; subsequently, however, they perforate and 
excavate them in order to form cells, into which they enter, and 
which they never quit afterwards. Once entered, their byssus ceases 
to grow§. 
One of them, the Mytilus lithophagus , L., Chemn., VIII, 
Ixxxii, 729, 730, is very common in the Mediterranean, where 
from its peppery taste it is esteemed as food. 
A second, Modiolo caudigera, Encyc. pi. 221, f. 8, has a very 
hard small appendage at the posterior extremity of each valve, 
which perhaps enables it to excavate its habitatation. 
Anodontea, Brag. 
The anterior angle rounded like the posterior, and that next to the 
* Add, Mytilus barbatus, L., Chemn., VIII, Ixxxiv, 7-19 ; — M. angulatus, Ib., 756 ; 
— M. bidens, Ib., 742, 745 \—M. afer, Ib., Ixxxiii, 739 — 741 ; — M. smaragdimis, Ib., 
745 ; — M. versicolor, Ib., 748 ; — M. lineatus, 753 ; — M. exustus, Ib., 754 ; — M. stria- 
tulus, Ib., 744 ; — M. bilocularis, Ib., Ixxxii, 736 ; — M. vulgaris, Ib., 732; — M. sex- 
atilis, Rumph., Mus. xlvi, D; — M. fulgidus, Argenv. xxii, D; probably the same as 
the Mya perna, Gm., Chemn., VIII, Ixxxiii, 738 ; — M. azureus, Ib., H ; — M. muri- 
nils, Ib., K ; — M. puniceus, Adans., I, xv, 2 ; — M. niger, Ib., 3 ; — M. Icecigatus, Ib., 
4, &c.: some of these, however, may be mei’e varieties. 
•f M. Brongniart has formed them into a subgenus by the name of Mytiloida, 
Ap. Cuv. Oss. Foss, tome II, pi. iii, f. 4. 
J Mytilus modiolus, Chemn., VIII, Ixxxv, 757 — 760, and that of Miill., Zool. 
Lan., II, liii, which appears to be another species ; — M. discors, Chemn., VIII, 
Ixxxiv, 764 — 768 ; — M. testaceous, Knorr., Vergn., IV, v. 4, &c. 
§ M. Sowerby doubts this fact, which is, however, well attested by M. Poli from 
ocular demonstration — Test. Neap., II, p. 215. The pi. xxxii of the same work, fig. 
10, 11, 12, 13, also proves that the animal resembles that of a Mytilus, and not that 
of a Pholas or a Petricola. 
The mode in which the Lithodomi, Pholades, Pctricolce, and some other bivalves 
perforate stones, has been the subject of much discussion; some of the disputants 
holding it to be eff'ected by the mechanical action of the valves, and others simply 
by solution. See the Mem. of M. Fleuriau de Bellevue, Journ. de Phys., an X, p. 
345 ; Poli, Test. Neap., II, 215, and Edw. Osier, Phil. Trans, part III, 1826, p. 
342. All things considered, the first of these opinions, whatever be the difficulties 
it presents, seems to us to come nearest to the truth. 
