TRACHEARI^E. 337 



The Pycnogonides are marine animals, analogous either to the 

 Cyami and the Caprellae, or to the Arachnides of the genus Phalan- 

 gium, where Linnaeus placed them. Their body is commonly linear, 

 with very long legs, composed of eight or nine joints, terminated 

 by two unequal hooks which appear to form but one, and the small- 

 est of which is cleft. The first segment of the body, which replaces 

 the head and mouth, forms a projecting tube, cylindrical or in the 

 form of a truncated cone, with a triangular aperture at its extre- 

 mity. The chelicera3 and palpi are placed at its base. The former 

 are cylindrical or linear, simply prehensile, and com posed of two 

 joints, the last of which is a forceps, the inferior finger or the one that 

 is fixed being sometimes shorter than the other. The palpi are fili- 

 form, and consist of five or nine joints, with a terminal hook. 

 Each of the following segments, the last excepted, bears a pair of 

 legs; but the first, or the one articulated with the mouth has a tuber- 

 cle on the back, on which are placed two eyes on each side, and 

 beneath, in the females only, two additional small folded legs, bear- 

 ing the eggs which are collected around them in one or two pellets. 

 The last segment is small, cylindrical and perforated by a little ori- 

 fice at the extremity. No vestige of stigmata can be perceived. 



They are found among marine plants, sometimes under stones 

 near the beach, and occasionally also on the Cetacea. 



PYCNOGONUM, Brun., Mull., Fab. 



The chelicerse and palpi wanting; length of the feet hardly greater than 

 that of the body, which is proportionably thicker and shorter than in the 

 following genera. They live on the Cetacea. 



PHOXICHILUS, Lat. 



The palpi wanting, as in the Phoxichili; but the legs are very long, and 

 there are two chelicerae. 



NYMPHON, Fab. 



The Nymphones resemble the Phoxichili in the narrow and oblong form of 

 their body, the length of their legs; and in the presence of chelicerse; but 

 they have, besides, two palpi. 



2 S 



