Phreatoicoides. 125 



spinules. Eyes not formed. Taking cephalon and pereion as 100, 

 pleon and telson measures -^'^. Fifth segment of pleon about 

 the same length as the anterior four. Sixth segment very 

 powerful, deeper than anterior ones, narrowly united to tifth 

 segment, measures with telson about the same length as the 

 anterior live segments. Upper antennae slightly less in length 

 than peduncle of lower antennae. Lower antennte about two- 

 thirds of the length of the body ; peduncle of five joints, first 

 two short, subequal, remaining three gradually increasing in 

 length, the last being as long as the first three combined. 

 Lower lip two-lobed. Extremity of inner lobe of first maxilla 

 clothed with three plumose setae, extremity of outer lobe truncate, 

 and bearing about nine spiniforra setie. Legs long, slender. 

 First pair (gnathopods) subchelate, largely developed in some 

 males. Telson abruptly truncate. Uropoda with peduncle, 

 stretching behind the telson ; rami as long as peduncle, inner 

 one curved inwards. 



Colour. — Creamy-white. 



Length. — 9-20 mm. 



Habitat. — Fresh-water runnel, Thorpdale, Gippsland. 



Detailed Desckiption. 



The following detailed description is mainly taken from a 

 male specimen 17 mm. in length, and a gravid female of 12 mm. 

 in length. 



Body (Plate X., Fig. I). — The largest specimen I have measures 

 20 mm., and the smallest 8 mm. A female with eggs in the 

 incubatory pouch measures 12 nim.^ 



The V)ody is very slender, and, within narrow limits, uniform 

 in width and depth throughout, except for being deeply cleft 

 ventrally at the junction of the tifth and sixth segments of the 

 pleon, which allows the posterior segment to be flexed acutely 

 downwards. This segment with its uropods acts as a powerful 

 lever to propel the animal forwards. 



The dorsal surface is very convex and the ventral surface 

 slightly so. 



1 In the lithograph, a mistake has been made in the terminal segment, where the 

 articulation of the uropod is made to appear as if with the anterior margin, instead of with 

 the postero-distal margin. Fig. 14 shows it correctly. 



