218 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



GENUS ACAMHOLEBERIS Lilljeborg. 



Body more or less quadrangular, head triangular, acute cephalad, 

 bearing the antennules at the front. Fornix slightly developed. 

 Head scarcely separated by a depression from the body. Antennules 

 elongate, expanded apically. The three-jointed branch of the antencte 

 has five set^e, the four jointed ramus has three, all being apical. The 

 seta of the basal joint of the three jointed ramus is elongate. Labrum 

 with an acute process. Feet six pairs. Intestine with a loop. Post- 

 abdomen broad, armed with a series of spines. Margin of the shell 

 with long spines below. 



Ancantholeberis curvirostris O. F. Miiller. 



Plate XLVI, Figs. 1-4. 



O. F. Miiller 1785 (Daphnia curTirostris); Schoedler '46 (Acanthocercus rigidus); 

 Lievin '48 (Acanthocercus rigidus); Lilljeborg 'S-*^, and '58 (ligida); Leydig '60 

 (rigidus); Norman '63; Norman and Brady '67; P. E. Maeller '68; Lund '70-'71; 

 Hellich '77. 



This rare species has not yet been found in America but may be 

 confidently expected. The aspect is raacrothroid, the whole ventral 

 margin being long ciliate, while from near the posterior angle aiisc a 

 number of greatly elongated selai. The caudal margins are armed 

 with short spines. The macula is present but rather small. The an- 

 tennules are elongate, expanded toward the tip, somewhat curved and 

 armed apically with about eight unequal lanceolate processes and 

 smaller spinules. The post-abdomen is broad, rounded distally. The 

 claws have two small basal teeth and a series of small setse. The pos- 

 terior margin is armed with a series of small teeth. Length less than 

 1.5 mm. 



GENUS OFRYOXUS Sars. 



Lyncodaplmia — Herric k. 



Body elongated, somewhat rectangular as seen from the side, great- 

 est width and height of shell a little posterior to the heart; head sepa- 

 rated by a depression from the body, truncate below; antennse and 

 antennules much as in Macrothrix; four jointed ramus of antenijiTe with 

 no lateral set*: eye small, pigment fleck present; intestine twice con- 

 voluted, expanded posteriorly, with anterior but no posterior cseca, 

 opening near the "heel" of the post-abdomen; post-abdomen large, 

 triangular; terminal claws long, rather straight, with two accessory 

 spines at the base. 



Ofnjoxus is, as was suggested, a curious transition form linking the 

 Da])hnidw with the Lynceidce. 



