TRACHEARI/E. 211 



culated 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, Brun., Mnll., Fab. 



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(l). 



Phoxichilus, Lat. 



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

 and there are two chelicerae(2). 



Nymphon, Fab. 



The Nymphones resemble the Phoxichili in the narrow and ob- 

 long form of their body, the length of their legs, and in the presence 

 of cheliceraej but they have, besides, two palpi(3). 



lateral expansions of the intestinal canal, or cxca. I have, in fact, observed traces 

 of them under the form of blackish vessels, in various Nymphones. This induces 

 me to believe that these animals respire by the skin, a character by which we 

 might form them into a particular order, and one perhaps intermediate between 

 the Arachnides and Apterous Insects of the order of the Parasita. 



(1) Midi. Zool. Dan., CXIX, 10 — 12, the female. Found on our coast by MM. 

 Surirey and d'Orbigny. 



(2) Refer to this genus the Pycnogonum spinipes of Othon Fabricius, his variety 

 of the P. grossipes, witliout antennae; the Phalangium aculeatum,- the spinosum 

 Montag., Lin. Trans.; the NympJion femoratum of the Acts of the Soc of Nat. Hist. 

 of Copenhag., 1797; the Nymphon hirtum. Fab., which perhaps does not differ 

 from the Phal. spinipes and spinosum above quoted. 



(3) Pycnogonum grossipes, 0th. Fab.; Mull., Zool. Daji., CXIX, 5 — 9, the fe- 

 male; to compare with the Nymph, gracile and femoratum. Leach, Zool. Miscell., 

 XIX, 1, 2. His genus Ammothea — A. carolinensis, lb. — differs from Nymphon in 

 the chelicerje which are much shorter than the mouth, the first segment or radical 

 joint being very small. The palpi consist of nine joints, while those of the Nym- 

 phones have but five. In this genus, as well as in Phoxichilus and Pycnogonum, tlie 

 second joint of the tarsi is very short. The tubercle on which the eyes are placed, 

 is sometimes situated on an elevation which projects above the base of the ante- 

 rior segment or die moudi 



