58 MYTILIDAE. 
of this family. We may have opportunities of again observing 
Mytilus, Modiola, and Crenella, but the animals of Pinna and 
Avicula are not met with on the South Devon coasts m 
my district of Exmouth; I should therefore be extremely 
obliged to malacologists who have opportunities of seeing 
these animals to communicate their remarks. I shall at pre- 
sent give a short account of them from Poli, which I trans- 
late from M. Deshayes’ extracts from that eminent zoologist, 
in the last edition of Lamarck’s ‘ Animaux sans Vertebres,’ 
to enable naturalists to compare and weigh well their rela- 
tions with each other, and with the families of the Mytihde 
and Ostreade. 
MYTILUS, Linneus. 
M. epuuts, Linneus. 
M. edulis, Brit. Moll. 11. p.170, pl. 48. f. 1-4, and (animal) pl. Q. f. 5. 
M. incurvatus, M. pellucidus, M. subsaxatilis, Auct. 
Animal elongated, thick, subeconical; at this season, 5th 
August, the general colour varies from white to all the hues 
of orange-yellow, except the foot, and the dorsal and ventral, 
posterior and anterior extremities of the mantle, which perma- 
nently exhibit the various shades of a deep reddish brown. 
The mantle is open from the very large, short, oblong oval, 
white, simple membranous tube, situated on the upper poste- 
rior slope, which serves for anal purposes, and a separate 
branchial communication by a transverse fissure in the im- 
ternal septum into the ventral cavity, which, though it com- 
municates with the same common tubular process as the 
rectum, has no further connexion with the anal conduit. 
The mantle has a double margin, a plain outer and an inner 
one, which, from the poimt of the siphonal tube to the centre 
of the ventral range, is furnished with tentacular dendroid 
cirrhi, 15-25, of a pale brown on the main stems, with the 
ramose subfoliated fimbrize shadowing to pale yellowish white ; 
the remainder of the ventral range, in which the byssus and 
foot act, is only broken into long white dentations; the two 
