Miscellaneous. 251 
marine animals of which they are commensals. Their food appears 
to be very varied, according to age and locality. 1t is the colour of 
the food which fills their stomach and marks its outlines, which, 
when seen by translucence, gives the coloration remarked in several 
species, for the integuments are transparent and of a nearly colourless 
testaceous-yellow tint. If my observations are correct, Halacarus 
spinifer, Lohm., the largest and commonest species of our coasts, 1s 
exclusively carnivorous in its youth; the larvee and nymphs are of 
a coral-red colour, identical with that of the ova of Copepods which 
abound in the region inhabited by them; the adult, on the con- 
trary, is of a darker or lighter brown, and we find in its stomach 
numerous tests of Diatoms, indicating at least a partially vegetable 
regime. Like many other Acarina, therefore, these animals are 
parasites in their youth, and become simple commensals when adult. 
The Halacaride live well in brackish water, and even resist fresh 
water for a long time. They can be kept alive for two or three days 
in an aquarium of the latter kind, while Copepoda die there rapidly. 
In the canal from Caen to the sea, the water of which has scarcely 
more than 2 gr. of salt in the litre, M. Le Sénéchal has found Hala- 
carus spinifer upon the Hydroids which have become acclimatized 
there. 
But it is in the Laminarian zone, or, more correctly, in the Coral- 
line zone, and especially upon Corallina officinalis, that these animals 
abound, as is shown by the numerous dredgings which M. EK. Chev- 
reux has been good enough to make specially at my request upon 
the coast of the Croisic. The Halacaride occur in great numbers 
attached by their hooked feet to the delicate fronds of the Corallines. 
In M. Chevreux’s flasks these animals are mingled with hundreds 
of small Crustaceans (Copepods, Amphipods, and Ostracods), with 
Pyenogonidze and specimens of Amphiwra squammata, collected at 
the same time. These results agree with those obtained by Dr. 
Lohmann in the Baltic; of the fitteen species collected by him two 
occur in the zone of red seaweeds (Corallines) at depths of 5-10 
fathoms. 
The number of species from the French coasts which I shall make 
known in a memoir now in course of preparation is comparatively 
considerable. My collection contains seventeen species, while the 
English naturalists have only recorded ten, and Dr. Lohmann fifteen. 
_ The individuals from the Ocean are superior in size to those of the 
Baltic, although several species are identical, such as Rhombognathus 
(Aletes, Lohm.) notops, R. Seahami, Halacarus spinifer (=H. cteno- 
pus of my previous note), H. Murrayi (=H. inermis), H. Fabricia, 
H., rhodostigma, and Leptognathus falcatus, which inhabit our At- 
lantic shores. 
Two generic types (Leptopsalis and Copidognathus) characterized 
in my former note occur in the Ocean and are wanting in the Baltic. 
A new species of the former genus (Leptopsulis Chevrewxt) will 
enable this type to be better characterized. It occurs at the Croisic. 
This applies also to Pachygnathus sculptus, Brady, a species which is 
very interesting as having been dredged at a depth of 35 fathoms. 
