4^8 



AKACIINIDA. 



vided with chelicerrc and palpi, or one kind of these organs) constitutes the month. ■■""' Both sexes have 

 eight feet, fitted for runDitig; but the females exhibit, besides, two false legs, situated near the anterior 

 pair, and only employed in carrying the eggs. These animals are marine, analogous either to Cyamus 

 and Caprellaf, or to the Arachnida of the genus Phalangium, with which Linnaeus united them. The 

 body is commonly linear, with \ery long legs, consisting of eight or nine joints, and terminated by two 

 unequal ungues, appearing only to form a single one, the smaller one being sht. The anterior segment 

 of the body, which replaces the head and mouth, forms a projecting tube, nearly cylindrical, or conical, 

 having a triangular or trilobed orifice at its extremity. It is furnished, at the base, with the chehcerK 

 and palpi. The former are cylindrical and linear, simply prehensile, 2-jointed, the terminal joint che- 

 liferous, with the lower finger, which is immoveable, sometimes very shnrt. Tlie palpi are filiform, 

 from 5 to 9-jointed, with a hook at tlie tip. Each succeeding segment, ^^ith tlie exceptiun of the last, 

 supports a pair of legs ; but the anterior of those with which the head is articidated, bears, on the 

 back, a tubercle, on which is placed a pair uf ocelh ; and on the under &ide, m the females alone, two 

 other slender legs, folded upon each other, and bearing tlie eggs, which are placed all round them in 

 one or two masses. The last segment is small, cylindrical, and pierced by a small orifice at the tip. 

 We can discover no vestiges of spiracles. RI. Edwards, who has observed these animals in a living 

 state, tells us that he has seen, in the interior of the feet, lateral expansions of the intestinal canal, or 

 coccums. I had also perceived the traces, under the form of blackish vessels, 

 in different Nymphons ; and hence I am induced to beUeve that these creatures 

 respire ];y the skin, — a peculiarity which w'ould render the establishment of a 

 di:>tinct order necessary, probably between the Arachnida and apterous para- 

 sitic insects. Tliey are found amongst marine plants, under stones near the 

 beach, and occasionally also on the Cetacea. 



Pycnogonum, Bninn., Miill., Fabr., is destitute of chelicerrc and palpi, and their V:^s 

 scarcely exceed the lent^th of the "body, which is proportionately shorter and thicker 

 than in the following genera. They live upon ^"\^^ak-'s. 



P/io.ric/ii/>ix, Latr., has no palpi, but the legs are very long, and they have two chelicera?. Pi/cno<junnm 

 sp'tnipcs, (). Fabr., — Ph. acideatum and splnosum of Montague, Traii.sactions of the Liuajjaii iSociciij, — NijmjiJiua 

 ffmonitum of the Acta of the Society of Natural History of Copen- 

 hagen, 1797, &c. 



Niimphoity Fabr., resembles the last in the very narrow and ob- 

 long form of the Ijndy, the length of the legs, and presence of cheli- 

 rerae ; but they have moreover two pal|)i, composed of five joints. 

 N. grossipes, O. Fabr., Miillcr, Zool. Dan. Compare, also, Leach, 

 Zool. Miscell. vol. iii. 19, f. 1, 2. 



Ammothea, Leach (A. carolinensis, Leacb), differs frnni Nymplion 

 in the cliclicerEe being much shorter than the mouth, the basal pie 

 being very small. Tlie palpi are 9-jointed. 



[From the apparent absence of breathing pores, Latreille, in bis ' 

 Coins d^Eiitomologie, forms these animals into a distinct order, — 

 Aporobranchia; but Leach had previously given to them the ex- 

 pressive name of Podosomata. There are several British species 

 described by Dr. Johnston in the Magazine of Zoology and Botany^ 

 No. iv., wherein several new genera are proposed. It will, howe^'er, 

 be necessary to change the names of some of them, as they are 

 already employed for genera of Crustacea. A still more extra- 

 ordinary genus, with ten legs, is described by Eights in the 

 Jioston JoariKd of Nafunil Il/starg, under tlie name of Dccalo- ^ 

 poda aunt rail ■•>.] 



Fig. 35, — Pjcnncomim (jnlo:— 



m|)hon grotisiptf 



THE THIRD FAMILY OF THE TRACIIEAN ARACHNIDA,— 



The Hoi.etra (Ilcrinanii), — 



Has tlie thorax and alxlomen imited into a mass, Ijencatli a common epidermis. The thorax is at most 



ihvided into two by a strangiihilion ; and the alidomen merely presents, in some species, the traces of 



articulations, formed hy foldings of the ciiido'mis. Tlie anterior extremity of the body is often ad- 



rhr ]tr,l|,i are tlicrrc those uf the ni 

 t A.eor'lid^r to Snvignj-. they lor 

 i'lo find Crustnco!!. I place them i 



