254 Part III.—Nineteenth Annual Report 
simple in structure and do not form grasping organs as in Cancerdla; 
the maxillipedes are more rudimentary ; and the thoracic feet, of which 
there appear to be only two pairs, are each composed of two moderately 
stout basal joints and a single biarticulated branch ; in Cancerilla the 
first and second pairs of feet, though two-branched, are more rudimentary 
than those of Cancerina, and the third and fifth pairs, though present, are 
also rudimentary. 
In consequence of these differences I have considered it necessary to 
institute a new genus for this Copepod, and, from its general resemblance 
to the Cancerilla of Dalyell, have given to it the name of Cancerina. 
NICOTHOID. 
Nicothoé astaci, Aud, and M.-Edw. (Pl. XVIL, figs. 35-39; Pl. XVIII, 
figs. 21-26.) 
1826, alee astacz, Aud. and M.-Edw., Ann. Sci. Nat., 
(1), vol. ix., p. 345, Pl. 49, figs. 1-9. 
1850. ‘Nivothos astact, Baird, Entom., p. 807, Pl. XXXIIL, 
figs LL. 
Description of the female.—The length of the specimen represented by 
the drawing is 1:5 mm. (about 4, of an inch), exclusive of the caudal 
sete. The body is cyclopoid in its general outline, but the two great 
wing-like lateral expansions of the posterior part of the thorax destroy 
the symmetrical appearance of the animal. These expansions appear to 
be the result of an extraordinary development of the fourth segment of 
the thorax. The three segments intermediate between this one and the 
cephalic segment are very narrow; they are represented on the dorsal 
aspect by more or less distinct articulations as shown in the drawing, 
while in front of the cephalic segment two distinct eyes can be observed. 
The abdomen is composed of four segments, the genital segment is some- 
what dilated and rather longer than the ¢éombined lengths of the next 
two segments. The caudal furca are very short, and each is furnished 
with an elongated and moderately stout terminal seta and a few minute 
hairs. The two ovisacs are very large. (Pl. XVII. fig. 39, and 
PL XV IMS fig. 21) 
The antennules are of moderate length and sparingly setiferous, they 
are composed of eleven joints, but, with the exception of the second and 
last, all the joints are small (Pl. XVIII., fig. 35). The formula shows 
approximately the proportional lengths of all the joints :— 
Numbers of the joints, Wie 2 ie Seby Ane ORO, a dee O25 00) an cee 
Proportionai lengths of the joints, 11.383 .13.10.10.10.10.10.10.10, 20 
The antenne are small but moderately stout, and appear to be com- 
posed of four joints, the basal joint is considerably larger than the others ; 
each antenna is armed with two moderately strong apical spines, and as 
the end-joint to which they are attached is hinged at nearly a right angle 
to the preceding joint, the antenne become, with the assistance of the 
apical spines, effective grasping organs; the third joint is provided with a 
curved and ssmewhat lamelliform plate, which may be a sensory appendage 
(Pl, XVIIL, fig. 36). 
The mandibles are long and slender, slightly incurved, and tapering to 
a point (Pl. XVIL., fig. 22), 
The maxille are each composed of a moderately stout basal joint, and a 
