no 1651. REPORT ON THE 08TRAC0DA—8HARPE. 411 



Seen from above (fig. 2), the shell is proportionately broader 

 than that of /. bradyi, being - about four-ninths of the length, while 

 with /. bradyi this proportion is about as 1 to 3. 



Anterior and posterior ends showing a number of prominent 

 tubercles, a prominent constriction just back of the region of the 

 eye-spot, and still another laterally just about the middle of the body 

 region. The posterior third of the shell is widest of all, but sud- 

 denly incurved dorsally, so as to cause an appearance of two very 

 decided rounded swellings of shell along postero-dorsal margin 

 (fig. 2). All these furrows and humps give the shell a decidedly 

 crumpled appearance; this appearance may vary somewhat from 

 the figure given, but, in the main, averages as shown. 



Natatory seta? of the second antennae reach about to tips of ter- 

 minal claws. Second foot as in /. bradyi. Furca very much as in 

 /. bradyi, except that the terminal seta is longer, it being approxi- 

 mately two-fifths length of terminal claw, or about two and one-half 

 times as long as the average width of furca, the subterminal claw 

 being slightly longer than the terminal one. These proportions 

 varied somewhat in different specimens, so that I am of the opinion 

 that both /. gibba and /. bradyi are very variable in details of struc- 

 ture, so much as to cause great confusion in diagnosis. 



I believe that Midler a very wisely chose to speak of these forms 

 as occurring under four variations, namely, with humps or without 

 humps, or with long natatory seta? (reaching beyond tips of end 

 claws) or short natatory setae (reaching not beyond base of end 

 claws). The terminal seta of the furca also seems to be somewhat 

 variable in length in the same species, as is also the length of the 

 subterminal as compared with the terminal claw. 



Described from a number of specimens kindly sent me by Prof. 

 A. E. Beardsley, which were collected by him in the same locality as 

 /. bradyi (Carters Slough, March, 1905). 



Distribution same as /. bradyi. 



17. ILYOCYPRIS BRADYI G. O. Sars. 

 Plate LVI, figs. 3-6. 



Ilyocypris bradyi Sars, Forh. Vid. Selsk., Christiania, 1S90, No. 1, p. 

 59.— Mulleb, Zoologica, XII, Heft 30, 1900, p. 90, pi. vm, figs. 9, 

 11-13.— K.u 1 mann. Revue Suisse de Z00L, VIII, 1900, p. 353, pi. 

 xxiv, figs. 1, 2; pi. xxv, figs. 17, IS. 



Dimensions of female. — Length, 0.85 to 0.95 mm. ; height, 0.45 to 

 0.5 mm. ; breadth, 0.32 to 0.5 mm. Male slightly larger. 



Seen from the side (fig. 4), the shell is about twice as long as high, 

 dorsal margin nearly straight, ventral rather decidedly sinuate, an- 



Zoologica, XII, 1900, p. 88. 



