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



and wrist. Krdyer in describing Eusirus cuspidatus, says that there are half a score of 

 spines on the outer plate of the first maxillse ; in the form which I have considered to be 

 Eusirus longipes, Boeck, there are eleven spines, but in each of the three species of 

 Eusiroides, after careful examination, I can only count ten. In Pleustes, if I may judge 

 from Pleustes abyssorum, which has some other points of resemblance to the genus 

 Eusiroides, there are also only ten spines on the outer plate of the first maxillse. 



Eusiroides csesaris, n. sp. (PI. LXXX VIII.). 



Rostrum small, carinate underneath, lateral lobes of the head rather prominent, flat in 

 front, rounded below, separated by an incision from the short straight remainder of the 

 lateral margin ; the first two segments of the pleon dorsally produced backwards, each in 

 a small sharp tooth, their postero-lateral angles produced in very small denticles, those of 

 the third segment not produced, the lower lobe of the hind margin denticulate, the upward 

 pointed denticles reaching almost to the top of it ; the first segment distally and the 

 second and third segments show only a suspicion of compression along the dorsal line, the 

 back of the animal in general being broadly rounded; the fourth segment of the pleon with 

 a transverse dorsal depression ; the integument showing in many parts a strong striation. 



Eyes large, reniform, not coming so near to one another at the top of the head, nor 

 retaining so dark a colour in spirits, as the eyes of the next species, Eusiroides pompeii. 



Upper Antennse. — First joint longer than the next two united, twice as long as broad ; 

 the second joint much narrower than the first, and broader than the third, which is 

 nearly half its length ; the first joint has some groups of stout spines on the surface, and 

 some mixed groups on the irregular apical margin ; the second and third joints have 

 some calceoli besides various groujis of setules ; the fiagellum thick at the base, of 

 seventy-four joints, is much longer than the peduncle ; the earlier joints are broader than 

 long, each having a large calceolus with attendant cilia and cylinders, the margins of the 

 joints assuming a sort of spiral arrangement which is followed by the calceoli, for which 

 there would not be room in single file ; on the later joints their size diminishes, and from 

 the slender terminal joints they are absent ; the secondary fiagellum, consisting of a 

 single narrow joint, is not so long as the short first joint of the primary ; its rounded apex 

 is tipped with four setules. 



Lower Antennse not so long as the upper; the first three joints short, the first not 

 expanded, the gland-cone inconspicuous, the second and third both more or less armed 

 with spines ; the fourth joint longer and broader than the fifth, carrying several groups 

 of setae and spines ; the fifth somewhat longer than the second of the upper antennse, 

 armed like the fourth, but also having calceoli ; the fiagellum of fifty-five or more joints 

 is thick at the base, most of the joints being much broader than long, armed as in the 

 upper antennaj, the first joint about as long as its breadth. 



