56 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.60 



acters stated in his text and portrayed in his drawings. By so doing, 

 however, it must not be inferred that the present author is convinced 

 of the validity of Hesse's species. As in all his work there are so 

 many flat contradictions in both text and figures that his species can 

 neither be accepted nor rejected with any certainty. Some future 

 investigator must finally decide as to their truth or falsity. Mean- 

 while they seem to valid ; and if so, may be distinguished as indicated. 



Genus ERGASILINA P. J. van Beneden. 



Ergasilina Beneden, Ann. Sci. Nat., ser. 3, vol. 16, p. 97, 1851. 

 ErgasiUna Valle, Boll. Soc. Adriatica Sci. Nat. Trieste, vol. 6, p. 67, 1880. 

 Ergasilina Stossich, Boll. Soc. Adriatica Sci. Nat. Trieste, vol. 5, p. 263, 



1880. 



Generic characters of fenude. — General body form long and 

 slender; head small and covered with a carapace; first and second 

 thorax segments fused and separated from the head, bearing two 

 pairs of legs; third and fourth segments free, each with a pair of 

 legs; genital segment no larger than the fourth segment; abdomen 

 one-jointed, strongly tapered; anal laminae lanceolate, without setae. 



First antennae five-jointed, destitute of setae; second pair with 

 two basal joints and a long and stout terminal claw. Maxillae 

 three- jointed, the terminal joint a small claw or spine, the penul- 

 timate joint armed with minute teeth. Four pairs of swimming 

 legs, uniramose, two- jointed, without setae, the terminal joint tipped 

 with spines. Egg strings unknown. 



Type of tJie genus. — Ergasilina rohusta P. J. van Beneden, mono- 

 typic. 



Remarks. — This genus was founded upon a single female ob- 

 tained by Beneden from the gills of the common European ray, 

 Trigon pastinaca Linnaeus. Ten years later, in his monogram, 

 Recherches sur la Faune littorale de Belgique, Crustaces (p. 149), 

 he reported that the genus Avas found regularly upon the gills of 

 this fish. In another monograph published in 1870 on Les Poissons 

 des Cotes de Belgique (p. 15) he recorded finding three specimens 

 upon the same host, and a fourth much smaller one, which was 

 possibly the male. 



Beneden's original description and figures are the only ones ever 

 published, and unfortunately they were quite imperfect. If, how- 

 ever, the statements and figures which he did give were correct, 

 there can be no doubt of the validity of the genus. The fusion of 

 the first and second thorax segments, the exceptional size of the 

 second antennae, and the fact that all the swimming legs are 

 uniramose and without setae full}' establish the genus, but such 

 peculiar characters make it all the more desirable that they should 



