ACEPHALA TESTACEA. 
107 
Panopea, Mesnard, Lagr. 
A stout tooth, anterior to the callous enlargement of the preceding 
subgenus, and immediately under the summit, which decussates a 
similar one on the opposite valve, a character which approximates the 
Panopeae to the Solens. A large species is found in the hills at the 
foot of the Appenines in so high a state of preservation, that it has 
been mistaken for a recent sea-shell * * * § . 
There is another fossil species, which may perhaps be separated 
from it, that is completely closed at its anterior extremity f . 
After these various modifications of the Myae, we may place the 
Pandora, Brug. 
In which one valve is much flatter than the other ; the internal 
ligament is placed transversely, accompanied in front by a projecting 
tooth of the flattened valve. The posterior side of the shell is elon- 
gated. The animal withdraws more completely into its shell than 
the preceding ones, and its valves shut more closely — its habits how- 
ever are the same. 
But a single species is well known ; it inhabits the seas of 
Europe 
Here also we find a group of some small and singular genera, 
such as 
Byssomia, Ouv. 
Where the oblong shell, which has no mai’ked tooth, has the opening 
for the foot at about the middle of its edge and opposite the summits. 
The Byssomiae also penetrate into stone, corals, &c. 
A species which is provided with a byssus, abounds in the 
Arctic Ocean §. 
Hiatella, Daud. 
The shell gaping, to allow the passage of the foot, near the middle 
of its edges ; but the tooth of the hinge is better marked than in the 
preceding genus. Ranges of salient spines are frequently observed 
on the hind part of the shell. They are found in sand, among Zoo- 
phytes, &c. 
The North Sea produces a small species 1|. 
* Alya glycimeris, L., Chemn., VI, iii. A neighbouring, but shorter species in- 
habits the Mediterranean. Another fossil species is found near Bourdeaux. 
-f- Panope de Faujas, Mesnard, Lagr. Ann. du Mus., IX, xii. 
Here should be the place of the Saxicava of M. F. de Bellevue, small Testacea 
which perforate stones. See Rois., VI, 441. 
J TeUina intequivalvis, Cheinn., VI, xi, 106, and for the animal. Poll, II, xv, 7. 
§ Alytilus pholadis, Miill., Zool., Dan., Ixxxvii, 1, 2, 3, or Alya byssifera, Fabr., 
Groenl. 
11 Solen minutus, L., Chemn., VI, vl, 51, 52, or Alya arc/ica, Fabr., Groenl., which 
appears to be the same as the Hiat. a une fente, Bose, Coq. Ill, -x.xi, 1 ; — the lliat. 
a deux fenles, Id., Ib., 2. 
