82 PROCEEDINGS OF THE NATIONAL, MUSEUM, vol.60 



Two pairs of biramose swimming legs and occasionally the rudi- 

 ments of a third and fourth pair. Egg strings short, eggs large and 

 not much flattened. 



Generic chaTacters of male. — Head separated from the thorax and 

 well rounded; entire thorax fused into a spindle-shaped or elongate 

 body, whose segmentation is often very obscure. Abdomen more or 

 less distinct, one-jointed; anal laminae much larger than in the 

 female and armed with spines. 



First antennae relatively longer and stouter than in the female; 

 second pair projecting in front of the cephalon, and tipped with 

 strong claws. 



Maxillipeds very long and slender, projecting far beyond the 

 margin of the head. Two pairs of swimming legs, uniramose and 

 one-jointed. 



Type of the genus. — Ilatschekia M'ppoglossi (Kroyer), first spe- 

 cies. 



KEY TO THE SPECIES. 



]. Head more ov less spherical, the first and second thorax segments forminj^ 

 a distinct neck; trnnk four to ten times the lengtli of the head 2 



1. Head angular or widened transversely, no neck ; trunk short and thick, from 



two to four times the length of the head G 



2. First and second thorax segments completely fused, the two longer than the 



head ; trunk cylindrical, lobed posteriorly 3 



2. First and second thorax segments completely fused, but less than one-third 

 the length of the head ; trunk ilattened, no lobes 4 



2. First and second thorax segments only partially fused, much shorter than 



the head ; trunk cylindrical, no lobes 5 



3. Second thorax segment wider than the head ; second legs visible in dorsal 



view; first antennae three-jointed 2.33 mm., linearis Wilson, 1913 



3. Second thorax segment narrower than the head ; second legs not visible in 



dorsal view; first antennae five-jointed 9.50 mm., hippoglossi (Kr0yer) 1837 



3. Head, first two segments and trunk the same width ; second legs visible in 



dorsal view ; first antennae not distinctly segmented. 



1.50 mm., sargi (Valle), 1882 



3. Second thorax segment wider than the head; no legs visible dorsally; first an- 



tennae tAvo-jointed 1.70 mm., hudegasme (Kr0yer), 1863 



4. Trunk as wide as the head, first and second segments narrower; sides of 



trunk smooth ; first antennae three-jointed 1.70 mm., oNonga Wilson, 1913 



4. First and second segments as wide as the head, trunk much wider, its sides 



undulate 1.75 mm., albirubra Wilson, 1913 



4. Trunk wider than the head, widest posteriorly, witli three rows of knobs 



on the dorsal surface 1.90 mm., scari (Kr0yer>, 1838 



4. Trunk as wide as head, first and second segments narrower; one sinus on 



either side; first antennae five-jointed 1 mm., pygmaea T. Scott, 1913 



5. Head with a short and blunt posterior process ; trunk six times as long as 



wide ; first and second segments not distinct. 



2.40 mm., comigera T. Scott, 1919 

 5. Head smooth, trunk ten times as long as wide ; first and second segments dis- 

 tinct and wider than the trunk 4 mm.. fe»uif< (Heller), 1865 



