\Fuly 24, 1873] 
nd both participating in a singular deficiency, the total 
Ibsence of eyes. One of these has been referred by Dr. 
. Willemoes-Suhm to his genus Deidamia, It agrees 
jwith the species described in my former report in all its 
Jeiding characters, although certaia marked differences 
must lead to a slizht modification of the characters of the 
genus as formerly defined. In Detdamia leptodactyla 
all the five pairs of ambulatory legs bear chelz, while it 
is a character of the typical Astacide that chelz are 
present on three pairs only. In the new species there are 
chelz on four pairs of the ambulatory legs, the fifth pair 
ending in simple curved claws. The two species agree 
with one another, and with Aszacus, in possessing a 
lamellar appendage at the base of the outer antennz, 
and with this they have the flattened carapace of 
‘Palinurus, These characters have not been hitherto 
observed in combination, and their so occurring seems 
to be a more valuadle generic character thau the variable 
one of the form of the limbs. The character of this 
genus will now stand thus :— 
Deidamia.—Cephalothorax flattened, with a com- 
pressed free lateral margin. A lamellar appendage at 
Fic. 3.—Hyalonema Toxeres, Wyville Thomson (Upper surface of 
sponge body). 
base of each of the outer antennz. Swimmerets, consist- 
ing of three joints with two palpi. No trace of eyes or of 
eyestalks. 
D. leptodactyla v. W.-S.—All 
bearing chelz., 
D. crucifer v. W.-S.—Four pairs of the ambulatory 
feet bearing chele. 
As in D. leptodactyla, not only are the eyes and eye- 
stalks absent, but there is no indication of a space for 
their accommodation in the position in which eyes are 
normally developed. 
Deidamia crucifer certainly differs widely in general 
appearance from the recent Astacidz, at the end of which 
family we should, however, be inclined to place it for the 
present, It has avery close resemblance to some fossil 
forms, particularly the varying species of the genus Zryon. 
It has been already remarked that Dezdamia, in its flat- 
tened cephalothorax, approaches the Palinuridz; in all 
the living members of that family, however, the first pair 
of legs are monodactylous, while in De‘damia they are 
the ambulatory feet 
i: 
NATURE 
247 
didactylous. The fossil genus Zvyon forms an exception 
in this particular among Palinurids, with which it has 
hitherto been arranged, and has the first pair of limbs 
didactylous, as in Dezdamia. It has not yet been ascer- 
tained whether Zvyox has a lamellar append we at the 
base of the outer antenne. If this appendage be absent, 
there is probably scar:ely sufficient ground for separating 
Deidamia generically from Eryon. It is very likely that 
when the recent deep-sea forms near the Astacide and 
Palinuridz come to be carefully correlated with the cre- 
taceous and Jurassic species, it may be necessary to 
establish an additional family. 
The second crustacean, although having little of the 
facies of the typical As¢aci, presents apparently no charac- 
ters of sufficient value to warrant its separation from that 
genus. 
Astacus zaleucus, v. W.-S, (Fig. 2), with its long com- 
pressed cephalothorax, flattened abdomen and unequal 
chelz, has at first sight somewhat the appearance of a 
Calianassa. 
The total length of the animal is 120 mm.; the 
cephalothorax, 50, and the abdomen, [60 mm. The 
Fic. 4.—Hyalonema (Lower surface). 
carapace is hard, and firm, though only slightly calcified. 
It is greatly compressed laterally, rising into a high arch. 
It terminates in front in a slender spiny rostrum, 8 
mm. in length. The rostrum is covered with a thick 
felting of hair, which extends backwards, forming two 
hairv triangles on the anterior part of the cephalothorax 
In front of the carapace, between its anterior and upper 
edge and the insertions of the antennz, in the position of 
the eyes in such forms as Astacus fluviatilis, there are 
two round vacant spaces which look as if the eyestalks 
and eyes had been carefully extirpated and the space 
they occupied closed with a chitinous membrane. The 
lamellar appendage of the outer antennz has teeth along 
its inner border. It extends to the midule of the second 
basal segme it of the antenna, which is remarkably long. 
The flagella of the outer antennz are 130 mm. in length. 
The inner antennz originate in a line with the outer, 
The funiculus is shorter, and the flagella, which are equal 
in length, are much shorter than those of the outer 
antenne, - r 
