CHAP. IV.] ST. THOMAS TO BERMUDAS. 241 
It agrees with the species described in the previous chapter in 
all its leading characters, although certain marked differences 
must lead to a slight modification of the characters of the genus 
as formerly defined. In Wdallemoesia leptodactyla all the five 
pairs of ambulatory legs bear chelee, while it is a character of the 
typical Astacidee that chelze are present on three pairs only. In 
the new species there are chelze on four pairs of the ambulato- 
ry legs, the fifth pair ending in simple curved claws. The two 
species agree with one another, and with Astacus, in possess- 
ing a lamellar appendage at the base of the outer antennee, and 
along with this they have the flattened carapace of Palinurus. 
These characters have not been hitherto observed in combina- 
tion in any recent form, and their so occurring seems to be a 
more valuable generic character than the variable one of the 
form of the limbs. The character of the genus will now stand 
thus: 
Willemoesia, n. g.— Cephalo-thorax flattened, with a com- 
pressed, free, lateral margin. A lamellar appendage at the base 
of each of the outer antennze. At least four pairs of ambula- 
tory legs bear chelze. No trace of eyes or of eye-stalks. 
W. leptodactyla, v. W..S.—AIl the ambulatory feet bearing 
chele. 
W. crucifer, v. W.-S.—Four pairs of the ambulatory feet 
bearing chelee. 
The single example dredged of W7llemoesia crucifer (Fig. 59) 
isa male. The total length is 42 mm. (cephalo-thorax 19 mm., 
and abdomen 23 mm.), and the extreme width of the cephalo- 
thorax 18 mm. The carapace is flattened and compressed lat- 
erally, and the flattened lateral portions are curved upward like 
wings. The lateral margins are denticulated, and divided by 
two deeper incisions into three parts, the first bordered by 
seven, the second by four, and the third by seventeen teeth. 
The surface of the carapace is granulated, not spiny, as in W. 
leptodactyla. Two ridges crossing one another in the middle 
