TRACHEARI^E. 319 



but one, and the smallest 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 extremity. 

 The chelicerse and palpi are placed at its base. The former are cylindrical 

 or linear, simply prehensile, and composed 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 filiform, 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 tubercle on the back, on which are placed two eyes on each side, and beneath, 

 in the females only, two additional small folded legs, bearing the eggs which 

 are collected around them in one or two pellets. The last segment is small, 

 cylindrical and perforated by a little orifice 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, Muller, Fabricius. 



The chelicerae 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. 



,' w 

 PHOXICHILUS, Latreille. 



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

 there are two chelicerse. 



NYMPHON, Fabricius. 



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

 their body, the length of their legs, and in the presence of chelicera?; but they 

 have, besides, two palpi. 



FAMILY III. 



HOLETRA. 



THE trunk and abdomen are here united in one mass, under a common 

 epidermis, or at most, the thorax is divided by a strangulation, and the 

 abdomen, in some, merely exhibits an appearance of annuli, formed by the 

 plicae of the abdomen. 



The anterior extremity of their body frequently projects in the form of a 

 snout or rostrum ; most of them have eight legs, and the remainder six. 



This family consists of two tribes. In the first or the PHALANGITA, Lat., 

 we observe very apparent chelicerse, which either project in front of the trunk, 

 or are inferior, and always terminating in a didactyle forceps, preceded by one 

 or two joints. 



