ACEPHALA TKSTACEA. 107 



Panopea, Mesnard, Lagr. 



A stout tootli, anterior to the callous enlargement of the preceding 

 subgenus, and immediately under the summit, Avhich 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 |. 



After these various modifications of the Myae, we may place the 



Pandora, Brag. 



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, Cuv. 



Where the oblong shell, which has no marked 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 sj^ines 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. 



* Mya glijcimeris, L., Cheran., 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. 



X Tellina incequivalvis, Chemn., VI, xi, 106, and for the animal, Poli, II, xv, 7. 



§ Mi/tUus pholadis, MiiU., Zool., Dan., Ixxxvii, 1, 2, 3, or Mi/a byssifera, Fabr., 

 Groenl. 



II Solen minutus, L., Chemn., VI, vi, 51, 52, or Mya arclica, Fabr., Groenl., which 

 appears to be the same as the Hiat. a unefente, Bosc, Coq. Ill, xxi, 1 ; — the liiat. 

 a deuxfenles, Id., lb., 2. 



