498 ‘ll iscellaneous. 
sulcato. Caput antice deflecum, fronte semicirculari marginato. 
Mandibule membranacee? Mazille cornee, lobo apicali in un- 
guiculum curvatum acutissimum producto. Antenne 9-articulate. 
Prothorax fere rotundatus, antice truncatus, medio profunde sul- 
catus. Elytra-apicibus setosis, singulo 4-sulcato. Pedes lati, com- 
presst, tibiarum apicibus angulatis. 
Cheetopisthes fulvus, Westw. Fulvus, nitidus, capite et prothorace 
parum castaneis, hoc angulis posticis basique transverse impresso, 
empressionibus setulosis. Long. corp. lin, 13.—Hab. in India 
Centrali. D. Boys. 
A memoir on the characters and geographical distribution of those 
groups in nature which are considered as typical of families, by 
G. R. Waterhouse, Esq., was also read, which led to an extended 
discussion on the geography of insects. 
MISCELLANEOUS. 
Apparatus of Hearing in Mollusks. By Dr. Frey. 
Tue observations of Dr. Frey have been especially directed to the 
embryo of Limneus stagnalis. ‘The auricular vesicle is not percep- 
tible in this mollusk until the singular rotatory movements of the 
embryo have ceased, and when the animal already crawls on the in- 
ternal side of its shell. It is easy then to observe, on the anterior 
part of the body, the rudiments of the tentacles, the eyes with their 
pigment, and the tongue with its characteristic epithelium. On 
each side of the base of the tongue are found the auditory vesicles. 
They are spherical, their contour is simple, and their diameter from 
Gg tos, ofaline. At first they appear to contain in their interior only 
a transparent liquid, and are then, like the eye, unconnected with 
the central parts of the nervous system. There are soon developed 
in the liquid one or two small corpuscles, the form, the size, and the 
oscillatory movements of which are quite similar to those of the 
otolithes of the perfect animal ; the vesicle which contains them pre- 
sents on its margin a double contour, resulting probably from the 
thickness which the sides acquire. The size of the otolithes is from 
zi> to z4, of a line ; their number slowly increases, and reaches to 
20 when the Limneus quits its shell; the diameter of the vesicle is, 
at this period, +}, of a line. By the side of the otolithes occur other 
smaller corpuscles, which often do not attain the size of 4, ofa 
line. The number of the otolithes and the size of the auditory vesi- 
cle continue afterwards to increase, at the same time that the ani- 
mal increases; in the adult state, from 100 to 200 otolithes may be 
counted, and the diameter of the vesicle varies from ;', to 5 of a 
line. ) 
The development of the auditory apparatus presents the same 
phenomena in Physa, Paludina and the terrestrial Gasteropods in 
general (Helix, Limar, &c.) ; the only differences are in the size of 
the parts. 
In the bivalves, the apparatus of hearing only contains a single 
otolithe of large dimensions, which fills the cavity of the vesicle. 
