350 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 39. 



dal, as long as the entire animal; eggs large and munerous. Male 

 unknown. 



Type-species. — Thersitina gasterostei. 



(Thersitina, Thersites and an ending denoting likeness.) 



Body flattened; head fused with the first thorax segment and the 

 ventral surface of the resultant cephalothorax reentrant, so that its 

 edges, with the bases of the first antennae and the first swimming legs, 

 form an effective prehensile disk. Free thorax often as wide as the 

 carapace; genital segment enlarged but little; abdomen small and 

 stunted. Basal joints of the first antennae enlarged, flattened, bent 

 sharply at a right angle, and furnished with a row of dense setae and 

 tactile hairs along their anterior margin. Second antennae trans- 

 formed into prehensile organs, with spines and roughened surfaces, 

 but much shorter and weaker than those of the Ergasilidae. First 



Fig. 39.— Mouth-parts of female Bomolochus teres, la, Labrum; lb, labium; md, mandible; 

 mx', FIRST maxilla; mx", second maxilla; mxp, maxdlliped. 



swimming legs strongly flattened, not used for locomotion as much 

 as for prehension; fifth legs uniramose, but with two or more joints, 

 each bearing setae. 



Species usually about twice the size of the Ergasilinae, namely, from 

 one to two millimeters in length. 



DESCRIPTION OF THE MOUTH-PARTS. 



Female. — ^Mouth- parts close to the second antennae. Labrum 

 considerably wider than long, with a roughened surface, projecting 

 prominently from the head and well defined (fig. 39), Labium 

 divided and consisting of a half projecting inward from either side, 

 the two often not meeting at the center. Mandible consisting of a 

 narrow, cylindrical basal joint, which is curved sharply backward 



