270 S. I. Smith — ^hnpJii.podvs genera, 



palpus is j^k'iidir, and the third segment is ubout four times as long 

 as l)ioad and a little shorter, hut scarcely longer than, the second. 

 The maxilUe are nearly as in E. diffortnix : in the first pair the 

 inner lobe is small and tipped with one or two setae only ;* in the 

 second pair the two lobes are nearly equally developed. The niax- 

 illipeds are essentially as in E. difformis. 



The gnathopods have essentially the same structure as in Erictho- 

 nias. The first (Plate Ila, figure 1) arealike in both sexes : the 

 merus is narrow, armed distally with numerous seta?, and its anterior 

 margin articulates with the proximal half of one edge of the triangu- 

 lar carpus ; the carpus is nearly as broad as long, the posterior edge 

 is armed with numerous setae and projects considerably beyond the 

 broad articiilation with the propodus ; the propodus is as long, but 

 somewhat narrowei- than the carpus, approximately oval in outline, 

 and thickly armed along the convex posterior edge with setaj and 

 small spines ; the dactylus is stout, slightly curved and apparently 

 not capable of comj)lete adduction to the edge of the propodus. The 

 second gnathopods in the female ai'e like the first except that the 

 dactyhis is, perhaps, slightly longer. In the adult male, however, 

 the second gnathopods (figure 2) ai"e enormously developed, as in 

 the males of Erictlum.ms. The basis is much stouter but scarcely 

 longer than in the first pair. The ischium and merus are of nearly 

 the same form and size as in the first pair, though the merus is 

 slightly longer. The carpus is more tlian twice as long and broad as 

 in the first j>air : the posterior edge is convex in outline, armed with 

 a few small fasciculi of seta^, and projects distally in a long and stout 

 spiniform tooth; the distal end is very broad, the anterior half only 

 is occupied by the articulation with the propodus, and the edge of 

 the posterior part projects in a prominent obtuse tooth near the 

 base of the propodus, while between this tooth and the great tooth 

 of the posterior angle there is a deep rounded emargination, the 

 border of which is armed with one or two small spines and numer- 

 ous stout setae. The propodus is nearly as long as the carpus, about 

 twice as long as broad, slightly curved, and the posterior, or prehen- 



* Boeck. Ohristiania Videnskabs-Selskabs Forhandlinger, 1870, p. 246 (166), and 

 Scandinav. og Arktiske Amphipoder, p. 598, describes the inner lobe of the first 

 maxilla in the Podocerinae, as destitute of setae (" lamina interiore parvula, ovali, setis 

 destituta "). This is not characteristic of all the species of the group, however, and 

 will not serve as a character for distinguishing Gerapm (as here restricted) from the 

 Podocerinae; for Boeck himself in the latter of the works above quoted, plate 28, 

 figure 3f, figures set;e upon this lobe of the first maxilla of Cerapus [Ericthonius] 

 abditus, and they are certainly present in Ericthonius difformis. 



