22 
MOLLUSCA. 
long, througli the lateral fissures of its shell ; they are productions of 
the mantle. 
The species most known Anomia <m/en<a^a, Forskahl. ; Cavo- 
lina natans, Abilgaard ; H. cornea, Lam. ; Cuv., Ann. du 
Mus., IV. pi. 59; and Peron, Ib., XV, pi. 3, f. 13. has a small, 
yellowish, semi-diaphanous shell, found in the Mediterranean 
and the Atlantic Ocean*. 
Cleodora, Peron. 
The Cleodorse, for which Brown originally created the genus Clio, 
appear to resemble the Hyalese in the simplicity of their wings, and in 
the absence of tentacula between them ; it is also probable that their 
branchiaj are concealed in tlie mantle ; their conical or pyramidal 
shell, however, is not cleft on the sides. M. Ray distinguishes 
Cleodora, properly so called, with a pyramidal shell, 
Creseis, with a conical and elongated shellf, 
CuviERA, with a cylindrical shell. 
Psyche, with a globular shell, and 
Eurybia, with a hemispherical shell. (;];) 
It is thought that we may approximate to the Hyalese 
Pyrgo, 
A very small fossil shell discovered by M. Defrance ; very thin, glo- 
bular, and divided by a very narrow tranverse cleft, except before, 
where it becomes a little widened(aj. 
* Add: Hyal. liuiceolata, Lesueur, Bullet., des Sc. June 1813, pi. v, f. 3; — Hyal. 
inflexa, lb., f. 4. 
N. B. The Glav.ciis, Carinuire, and Firolc, referred by Peron to the family of the 
Pteropoda, belong to the Gasteropoda ; the Fhilliroe of the same author also 
probably belongs to it. — His CaUianire is a Zoophyte. 
•h It is probably near the Creseis, and perhaps even in the same subgenus, accord- 
ing to Messrs Rang and Audouin, that we must place the genus Triptera of 
Messrs Q,uoy and Gaymard, which is referred by M. de Blainville to the family of the 
Akerae. 
X See the M^m., of M. Rang, Ann, des Sc. Nat., Novemb., 1827, and March 1828. 
N.B. Several Pteropoda have been discovered in a fossil state. M. Rang has 
found, near Bourdeaux, Hyalete, Cuvieria, and Cleodorce. See Ann. des Sc. Nat- 
August 1826. The Vaginella of Daudin is a Cresis according to M. Rang; it has, 
in fact, all the characters of the latter. 
(a) The Pteropodes constitute the first order of Lamarck’s twelfth class, and 
his division of this order into genera, is precisely the same as that given in the pre- 
sent work, with the exception of the fossil genus added by Cuvier under the name of 
Pyrgo. The general description of the order by Lamarck is as follows 
These Mollusca have no feet to crawl with, or arms to assist their motion or seize 
their prey ; they have two opposite and simularly constructed fins adapted to swim- 
ming; their bodies are free and floating. The Pteropodes are swimming Mollusca, 
without the means of affixing themselves to other bodies, floating on the surface of 
the sea and changing their position by means of their two fins or oars, which resem- 
ble two wings placed on each side of the mouth in some and in others on each side 
of the neck. He adds that in the Ayalda the head is so much concealed at the base 
or point at which the fins are united that it appears obsolete, exhibiting consequently 
an alliance between these animals and the Conchiferee (the eleventh class of Mollus- 
cous animals in his system). In the Cymbulia a little lobe which stands forward on 
the posterior part, between the two true wings, has been erroneously regarded as a 
third fin. — Eng. Ed. 
