664 THE VOYAGE OF H.M.S. CHALLENGER. 



Length of the specimen in its bent position about one-fifth of an inch. 

 Locality. — The label on the mounted specimen states that it was taken 400 miles 

 north of the Sandwich Islands ; probably near Station 256. One specimen. 



Remarhs. — The differences between this species taken in the North Pacific and its 

 congener from the South Pacific and South Atlantic are obvious ; the shape of the first 

 segment of the pera3on and its size in comparison with the head, the armature of the 

 second gnathopods, the form of the fourth pair of side-plates, and, above all, the first 

 joint in the third pergeopods, afi"ord clearly distinguishing marks. It will be noticed that 

 it is in the smaller species that the third peraeopod has its most striking development, 

 precluding any probability that this species might be a younger stage of the other. 



Genus Cyclocaris, n. gen. 



Mandibles broad in front, molar tubercle not dentate, palp central. 



First Maxillie vnih. the inner plate bearing more than two plumose setae, spines of 

 the outer plate slender, teeth of the palp few. 



Second Maxillse with the inner plate much shorter than outer, a large part of its 

 inner margin fringed with setae. 



Maxillipeds with the inner and outer plates very broad, the outer with spaced 

 denticles on the inner margin, spine-teeth and setae round the apex and part of outer 

 margin ; these plates reaching as far as the apex of the second joint of the palp. 



Upper Antennse with the peduncle very short. 



Lower Antennse with the base not covered by the side-plates of the peraeon. 



Gnatho2wds very slender and very long. 



Side-plates of the first two perseon-segments very small. 



Third Uropods with long rami extending much beyond the other pairs. 



Telson long, extending much beyond the peduncles of the third uropods, deeply cleft. 



The generic name is derived from kvkKo's, a circle, and Kapa, head, it seeming 

 probable, from the structure of the side-plates, that the animal naturally coils itself into 

 a circle, bending its head round to the protection of the side-plates of the third and fourth 

 perseon-segments. The form of the name also points to the afiinity between this genus 

 and Cyphocaris of Liitken and Boeck. 



Cyclocaris tahitensis, n. sp. (PL XVIII.). 



Head short, lateral margin sinuous, bowed out between the upper and lower antennae ; 

 the side-plates of the peraeon not extended forward over the head or base of the lower 

 antennae ; the last four segments of the perajon rather long ; of the pleon-segments the 

 postero-lateral angles of the first rounded, of the second acute, of the third blunt, lower 



