78 Miscellaneous. 
is a very peculiar one, a strong rapid current running over a gravelly 
bottom : in such exposed situation our Unios do not often attempt 
a lodgement, but prefer sandy bars or muddy shores where the water 
is not very deep or rapid. Upon these gravel beds, however, the 
large shells are imbedded, and the young ones spin the byssus by 
which they attach themselves to the larger shells or the stones of 
the gravel. In this way I have seen hundreds moored and riding se- 
curely at anchor at the utmost tension of their lines ; for it is only, 
as far as I can perceive, a single filament. The thread appears to be 
attached to the mantle, and is probably produced by it, and is not an 
umbilical attachment. I saved some of the animals in spizits.”— 
Letter, 16th May, 1840. 
This account is curious in several particulars; first, as showing 
the relations of these animals to the family of Arcade; second, as 
showing what I have long expected from the observations I have 
made on some marine gasteropodous mollusca,—that many, if not 
most of the kinds, have the power of forming a byssus when it can 
assist them in their habits. It is very desirable, however, that the 
place where the byssus is attached to the animal should be re- 
examined, for if it takes its origin from the mantle, it is an ano- 
maly in the organization of mollusca. It always arises, as far as I 
am aware, from some part of the foot, in general from the anterior 
part of the base, as in Mytilus, Pinna, Avicula, Pecten, &c., but some- 
times from the end of this organ, as in Arca, from whence also, I 
should suspect, it most probably arises in the Uniones.—J. E. Gray. 
ON SOME RECENTLY PROPOSED GENEKA OF THE VIV ERRIDZ. 
To the Editors of the Annals and Magazine of Natural History. 
GenTLEMEN,—You did me the honour of reprinting in your ‘ Annals 
of Natural History’ for March, 1840, a short paper on the Crania and 
Dentition of the Carnivora, which I communicated to the Zoological 
Society. My object, as stated in that paper, was merely to point out 
a few simple characters by which the groups might be distinguished, 
the importance of those characters being confirmed by others exhi- 
bited, both by the internal anatomy and external structure of the spe- 
cies. Since the publication of that paper, M. Isidore Geoffroy* has 
furnished us with figures and descriptions of. some interesting ge- 
nera of Carnivora from Africa and Madagascar, which, according to 
my views, should be added to those already included in my list of 
the Viverride. They consist of the genera Ichneumia, Galidia, and 
Galidictis. The first of these (Ichneumia) belongs to that subdivision 
of the Viverride in which there is a complete bony orbit, and is 
founded upon three species described originally as species of the ge- 
nus Herpestes or Ichneumon. 'The other two genera (Galidia and 
Galidictis}), in the straightness of the lower margin of the rami of 
* See the ‘ Magazin de Zoologie’ of M. F. E. Guérin-Meneville, Parts 
9 and 10 for 1839. An extract of this paper appeared in the ‘ Comtes 
Rendus,’ &c. for October, 1837. 
+ In the original paper Galiciis. The alteration in the name was neces- 
sary, Mr. Bell having given the name Galictis to a group of the Mustelide. 
