590 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 55. 



maxillipeds well developed and tipped with strong claws ; one pair of 

 swimming legs close behind the maxillipeds. Male unknown. 



Type of the genus. — Opimia exilis Wilson, monotypic. 



{Opimia, a vestal virgin unfaithful to her vow.) 



Remarks. — \A^ien first established this genus was placed with the 

 Lernaeidae, since its near relatives belonged there. But at the re- 

 vision of the Lernaeidae ^ it was decided that Opimia and its rela- 

 tives could no longer remain in the family, and accordingly the pres- 

 ent new family has been formed to include them. Opim^ia is very 

 close to Trypaphyhim and the new genus Paeon.^ and the three differ 

 from Sphyrion and Rehelula chiefly in the fact that the posterior 

 processes are unbranched and are not covered with respiratory cylin- 

 ders or cones. The distinguishing character of the genus are the 

 smooth cephalothorax without processes or horns, the stout maxilli- 

 peds, and the single pair of swimming legs. 



PAEON, new genus. 



External generic characters of female. — Body separable into three 

 regions — cephalothorax, neck, and trunk; cephalothorax enlarged 

 into a transverse ellipsoid whose surface is produced into paired proc- 

 esses. Neck slender and nearly straight, but showing considerable 

 torsion. Trunk swollen, flattened dorsoventrally, and furnished 

 posteriorly with a pair of long and slender processes dorsal to the Qgg 

 strings; abdomen minute with a pair of globular anal laminae, and 

 completely fused with the genital segment. Egg strings straight; 

 eggs multiseriate. No antennae visible; proboscis retractile; a pair 

 of biramose maxillae on the sides of the mouth tube; a second pair 

 of maxillae behind the mouth, one-jointed and armed with stout 

 claws; no swimming legs. 



Internal generic characters of female. — Esophagus inclined and 

 entering the stomach on its ventral surface near the anterior end ; 

 stomach not much enlarged, without lobes or processes, passing in- 

 sensibly into the intestine, which is filose in the neck, is enlarged, 

 but without processes, in the trunk, where it is nearer the dorsal sur- 

 face, and is contracted into a short rectum, which opens between the 

 anal laminae. Ovaries paired, at the sides of the genital segment in 

 front of the cement glands; oviducts coiled transversely, the coils 

 kept in place by strands of dorsoventral muscles. Cement glands 

 at the posterolateral corners, close to the body wall, unsegmented, 

 with short ducts. Body wall thin and not chitinized. 



External generic characters of male. — Cephalothorax elongate and 

 covered with a carapace ; second thorax segment well separated ; 

 third, fourth, and fifth segments fused more or less completely, and 



1 Proc. U. S. Nat. Mus., vol. 53, pp. 1-150. 



