HYDEACAEINA : THE GENUS EYLAIS LATR. 109 



The distal end of tlie flexor surface bulges out, and is furnished 

 with ten or more spines, some with a tendency to be pectinate. 

 The fourth segment is about double the length of the third ; 

 it is more slender and tapers slightly at the distal end ; on its 

 flexor surface there are two longitudinal rows of strong, slightly 

 curved spines. The fifth segment is barely half the length of 

 the fourth; slightly tapered distally, it shows a tendency to 

 curve on the flexor surface and terminates in three short spines. 



The sides of the capitulum spread out anteriorly so as to form 

 a broad shoulder where the palpi spring from it ; the anterior edge 

 has a moderately deep cut into it. The anterior processes are 

 strong, with their distal ends broadened out. They are directed 

 towards the posterior, but do not go so far as the base of the 

 posterior pair, which are short and broad with their ends broad- 

 ened out and bluntly rounded. The mouth is almost circular with 

 a broad outer ring. The maxillary plate is almost entirely covered 

 by large pores. The pharynx is broad with the pharyngeal ridge 

 set so far back as to make the metapharyngeal area rather in- 

 significant. The air sacs are slender, slightly inflated and curved 

 at the distal end. 



The epimera occupy the anterior half of the ventral surface. 

 The first two pairs are fused together for the greater part of their 

 length, but they are separated a little at the outer extremity. 

 The third and fourth pairs are so hinged together at their inner 

 extremities that they leave a large triangular space between 

 them. The epimera, of which the third pair are the broadest, are 

 built up of a chitinous trellis-work framed by a thick chitinous 

 border. 



The legs are relatively short and thin. The first pair may attain 

 a length of 2*6 mm., and the fourth pair 3"4 mm. The fourth 

 pair of legs are without swimming hairs, but are well furnished 

 with pectinate bristles of which the first two pairs of legs also 

 possess a considerable number. 



The anus lies near the middle of the ventral surface, and is pro- 

 tected by a thick chitinous ring, while the genital area lies between 

 the first pair of epimera. 



Piersig gave some information relative to the life-history in 

 Zoologica, xxii., but this must be accepted with some reserve, 

 because at the time several species were grouped under the one 

 name extendens, and thus it is quite possible that more than one 



