ACEPHALA TESTACEA. 105 
near the lunule, is a little plate en chevron. The tubes are united 
and short * * * § . 
Some of them are found on the coast of France. 
In the Lavignons, the lateral plates are almost effaced, but a single 
small tooth is observable near the internal ligament ; there is also a 
second and internal ligament. The posterior side of the shell is 
the shortest ; the valves are somewhat open, and the tubes are sepa- 
rate and very long, as in the Tellinye. 
There is one found on our coast, Mija hispanica, Chemn. VI, 
iii, 21, which lives in the ooze at the depth of several inches f. 
FAMILY V. 
INCLUSA +. 
The mantle open at the anterior extremity, or near the middle 
only, for the passage of the foot, and extended from the other end 
into a double tube, which projects from the shell, whose extremities 
are always gaping. Nearly all of them live buried in sand, stones, 
ooze, or wood. Those of the genus 
Mya, Lin. 
Have but two valves to their oblong shell, the hinge of which varies. 
The double tube forms a fleshy cylinder, and the foot is compressed. 
The different forms of the hinge have furnished Messrs. Daudin, La- 
marck, &c., with the following subdivisions §, in the first three of 
which the ligament is internal. 
Lutrakia, Lani., 
The Lutrariis, like the Mactrse, have a ligament inserted into a 
large triangular cavity of each valve, and before that cavity a small 
* After abstracting tbe Lavignones and Lutrarice, tlie genus Mactra of Ginelin 
may remain as it is ; the species, however, are far from being well distinguished. 
Add, Mya australis, Chemn., VI, iii. 19, 20. 
The Erycin.e, Lam., are neighbours of the Mactra, and are but badly charac- 
terized. See Ann. du Mus., IX, xxxi, and Deshayes, Coq. Foss., I, vi ; part of 
them, perhaps, belong to the Crassatellae. The Anphidesm^e. Lam., or Ligul.e, 
Montag., appear to approach the Maetrae, but they are too imperfectly known to 
have any distinctive character assigned to them. 
-f- Improperly called by Gmelin Mactra piperata. 
Add, Mactra papyracca, Chemn., VI, xxiii, 231 ; — Mact. complanata, Id., xxiv, 238 ; 
— Mya nicobarica, Id., iii, 17, 18. 
J; M. de Blainville makes two families of this one, his Pvloridea and Adesma- 
CEA. The last includes Pholas, Teredo, and Fistulana; the first, all the others, and 
even Aspergillum. There are numerous genera established in this family too slightly 
characterized to permit us to adopt tliem. 
§ N.B. Half the Myse of Gmelin neither belong to this genus, nor even to this 
family, but to A’ulsella, Unio, Mactra, Xc. 
