GASTEROPODA TECTIBRANOII ATA. 
47 
dinal emargination excepted, that leads to the branchia% whicli liave 
DO mantle to cover them, hut are otherwise like those of the Aplysia? 
as well as the rest of their organization^. In the^ 
Bursatella, Blainv. 
The lateral crests are united in front in such a manner as only to leave 
an oval aperture for the transmission of water to the branchiae, which 
are also deprived of a protecting mantle*. 
These two genera, however, probably form but one. 
Akera, Muller. 
Have their branchiae covered, as in the preceding genera, but their 
tentacula are so shortened, widened, and separated, that they seem to 
be totally wanting, or rather to form a large, fleshy, and nearly rec- 
tangular shield, under Avhich are the eyes. Independently of this, 
the hermaphroditism of these animals, the position of their genital 
organs, the complication and armature of their stomach, and the 
purple liquid effused by several of their species, approximate them to 
the Aplysiae. The shell, of such as have any, is more or less convo- 
luted, but Avith little obliquity, and is without a projecting spire, 
emargination, or canal ; the columella, projecting convexly, gives a 
crescent-like figure to the aperture, the part opposite to the spire being 
ahvays the broadest and most rounded. 
M. de Lamarck names those in Avhich the shell is concealed in the 
thickness of the mantle, Bvlljea (a). It has but very feAv whorls, 
and the animal is imich too large to be draAvn into it. 
Bullcea aperta, Lam. ; Bulla aperta and Loharia quadriloha, 
Gm. ; Phylme quadripartita, Ascan. ; Mull., Zool. Dan., Ill, pi. 
ci. ; Blanc., Conch. Min. Not., pi. xi ; CuA^, Ann. du Mus. t. I, 
pi. xii, 6f. (The Sea Wafer), the animal is Avhitish, and about 
an inch long ; the fleshy shield, formed by the A'estiges of its 
tentacula, the lateral SAA'^ellings of its foot, and the mantle occu- 
pied by the shell, seem to diAude its upper svirface into four 
lobes. Its thin, Avhite, semi-diaphanous shell, is nearly all aper- 
ture, and its gizzard is armed Avith three very thick rhomboidal 
♦ Bursatella Leachii, Blainv., Malac., pi. xliii, f. 6. 
N.B. Authors have also approximated to the Aplysiae the rmdis, Montag., 
Lin. Trans., VII, pi. vii, which forms the genus Actj£ON of Oken, and which is at 
least closely allied to the Elysie tiinide, Risso, Hist. Nat. Mer., IV, pi. i, f. 3, 4 ; 
as I am not acquainted with the branchiae of either, I cannot class them. 
f The Sonnet, Adans., Senegal, pi. i, f. 1, is a species closely allied to Bullaea; 
but I cannot establish a genus, or even a species, upon so imperfect a document. 
( 5 ^ (aj There are other reasons than those above-mentioned for the measure 
employed by Lamarck. The shell of Bulla Aperta is not only slightly concave, but it 
is very thin and fragile, and partially roOed inwards on itself. Indeed we may adduce 
Lamarck’s division of the Linnsean genus bulla as a very happy specimen of the vast 
superiority of the natural over the artificial system, for up to the time at which he 
separated it into Bullisea, Ovula, Physa, Terebellum, and Achatina, and adding the 
remainder of Bulla to the genera Pysula, and Bulimus, the Linnaean genus was a 
combination of the most discordant elements. Such as marine, fresh water, and 
land shells. — Eng. En. 
