of the Oenus Ktysifrom Celebes. 359 



of the species brouglit back by the ' Challenger,' A. sulcatipes 

 is 68 millim. long, A. serrata 37 millini., A. hisulcata, (^ 23 

 millim., $ 35 millim. The species from Lake Tondano is 

 never more than 25 millim. in length. The largest females 

 were 25 millim., but the average size of the females bearing 

 ova was only 20 millim. The males are a little smaller and 

 average 18 millim. in length. With these preliminary re- 

 marks, which justify the step I have taken in making a new 

 species for it, I will proceed to describe its characters in 

 detail. 



The carapace is smooth and is not carinated dorsally until 

 near the rostrum. Tiie rostrum is sharp, laterally com- 

 pressed, and bears on the dorsal side from twelve to seven- 

 teen serrations and on the ventral side very constantly nine. 

 Occasionally there are a few hairs between the serrations, 

 but more generally they are absent. The rostrum does not 

 extend so far forward as the anterior end of the antennary 

 plate. Just above the antennary termination of the branchio- 

 cardiac furrow the carapace bears a small tooth. 



The pleon is smooth dorsally, compressed laterally, and the 

 sixth somite is always considerably longer than the tifth (from 

 once and a half to twice as long). The telson is long and 

 pointed, reaching very nearly as far as the ends of the swim- 

 merets ; it bears four little hairy patches on each side and 

 is terminated by a row of seven or eight short coarse hairs. 



The eye-stalks are short and the eyes are but little larger 

 in diameter than the stalk. 



The three basal joints of the first pair of antennas are 

 fringed with long stiff hairs standing out at right angles to 

 the joints ; the first joint is provided with a long stylocerite 

 almost as long as the second joint, and the second joint is 

 also provided with a stylocerite, but a short one. The two 

 long slender flagella are approximately equal in length and 

 about as long as the carapace, i. e. 7 millim. The second 

 antenna bears a broad ovate scapocerite, which is fringed 

 internally with stiff'-jointed hairs and extends forwards just 

 beyond the anterior termination of the rostrum. The flagel- 

 lum is about the same length as the body, i. e. 20 millim. 



The mandibles (fig. 3) bear no palps. The free edge con- 

 sists of a molar process (a), a short portion bearing coarse 

 feathered hairs (?>), a longer portion bearing much finer hairs 

 (c), and a grinding- process [d) marked with very tine parallel 

 ridges. 



The first pair of maxilla? (fig. 4) are small, foliaceous, and 

 divided into three branches. The outer branch or endo- 

 podite {end.) is tipped with one or two stiff feathered hairs. 



25* 



