254 Part III. — Nineteenth Annual Report 



simple in structure and do not form grasping organs as in Cancerilla) 

 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 Daly ell, have given to it the name of Gancerina. 



Nicothoid^e. 



Nicotine astaci, Aud. and M.-Edw. (PI. XVII., figs. 35-39 ; PI. XVIII., 

 figs. 21-26.) 



1826. Nicothoe astaci, Aud. and M.-Edw., Ann. Sci. Nat., 



(1), vol. ix., p. 345, PI. 49, figs. 1-9. 

 1850. Nicothoe astaci, Baird, Entom., p. 307, PI. XXXIII., 



fig. 11. 



Description of the female. — The length of the specimen represented by 

 the drawing is 1 "5 mm. (about Jy of an inch), exclusive of the caudal 

 setae. 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 combined 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 XVIII., 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, 1.2. 3. 4. 5. 6. 7. 8. 9. 10. 11 



Proportional lengths of the joints, 11 . 33 . 13 . 10 . 10 . 10 . 10 . 10 . 10 . 10 , 2Q 



The antennae 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 antennae become, with the assistance of the 

 apical spines, effective grasping organs ; the third joint is provided with a 

 curved and somewhat lamelliform plate, which may be a sensory appendage 

 (PI. XVIII., fig. 36). 



The mandibles are long and slender, slightly incurved, and tapering to 

 a point (PI. XVII., fig. 22). 



The maxillae are each composed of a moderately stout basal joint, and a 



