THALASSINID^, ASTAClD^E. 193 
fig. 13, Cuba : differs from the typical species by the lamellar shape of its 
natatorial feet and by its flat rostrum. 
Gehia spinigeraj sp, n., S. Smith, Rep. Peab. Ac. 1869 (1871), p. 92, 
Corinto in Nicaragua, and Gulf of Fonseca. 
AsTACIDiE. 
Astacus fluviatilis. The process of spawning and the fecunda- 
tion by sperraatozoids of the eggs whilst adhering to the lower 
side of the abdomen of the female is described by S. Chantran, 
C. R. Ixxiv. pp. 201 & 202, and J. Zool. i. pp. 356-358, abstract 
in Ann. N. H. (4) x. pp. 173 & 174. 
The habits, anatomy, moulting, and breeding of the common 
crayfish are described with many details by Steffenbekg, Bidrag 
&c. pp. 19-27, 28, 35, 36, 59, & 60-72. Eels are said to be great 
destroyers of crayfish in Sweden, but there are several instances 
of streams in which both abound ; soiling the water with saw- 
dust is said to make the crayfish disappear (pp. 23-25 & 28) ; 
the function of the stomach-teeth in grinding the food is 
defended against tEsterlen (p. 36) ; the " lapilli cancrorum,^^ or 
so-called eyes,^^ are considered to be formed by calcareous 
matter reabsorbed from the shell when preparing for the moult, 
and to constitute a provisional deposit until again consumed for 
the hardening of the new shell (pp. 48-56) . Full-grown indi- 
viduals moult once in the year, but younger ones several times 
(pp. 57 & 58). Copulation takes place in Sweden in October, 
and is continued sometimes until November ; but the females 
breed only every other year, the eggs not maturing sooner^ 
they hide themselves after fecundation, so that, during the 
winter, only males or sterile females are caught (pp. 63 & 64) ; 
incubation, or the time during which the eggs are fixed to the 
underside of the abdomen of the female, occupies in Sweden 
7 or 8 months, in more southern countries less (p. 68) ; the 
newly hatched young differ only in size, the form of the tail- 
fin, and the want of generative organs, from full-grown indivi- 
duals (pp. 70 & 71). They have a length of about 8|^ raillims., 
not including the claws, after the first moult 11 millims., after 
the second 13 millims., and after the third 15 millims. (p. 72). 
Its geographical range extends in Norway only to the south-eastern dis- 
tricts, and in Sweden as far north as the provinces Wermland, Dalame, 
Helsingland, and Gestrikland, 60°-62° N. lat. ; it is wanting in the larger 
rivers and in the large lakes (as, for instance. Lake Wettern, and now also 
Lake Wenern), is very rare in the Malar I^ake, and has been found only once 
in the inlets of the Baltic on the Swedish coast. It is very probable that it 
is not indigenous to these countries, but has been introduced by man in the 
latter half of the sixteenth century, as it is not mentioned before 1666, and, 
by an order of King Johann III. in 1574, carp and crayfish were to be brought 
from Germany. Id. 1. c. pp. 6-17, 25. 
