AMPHIPODA, 223 



that they will cut the threads that keep them there, in 

 order to precipitate them into the mud, where they may devour 

 them at their leisure. They appear to hreed during the whole 

 summer, as females carrying their ova are to be met with at 

 various periods. \Vad-rs and different Fishes prey upon them. 

 For these interesting obsen at i oi IN \ve are indebted to M. D'Or- 

 bigny, Senior, conservator of the Rochelle Museum and corre- 

 !.'; lumber of that of Paris *. 



Tin- second section HETEROPA, Lat. is composed of those with 

 fourteen feet, the last four of which, at least, are unarmed and destined 

 for natation only. It comprises two subgeneraf. 



PTERYGOCERA, Latr. 



The thorax divided into several segments; four antennae furnished 

 with setae or hairs in bunches; all the feet natatory and the last large 

 and pinnated J ; cylindrical, articulated appendages to the posterior 



extremity of the body. 



APSEUDES, Leach. EUPHEUS, Risso. 



The thorax also divided into several segments, but the two anterior 

 feet terminated by a didactyle forceps ; the two following ones clavi- 

 form, ending in a point and dentated on the edges ; the next six 

 slender and unguiculated at the extremity ; the last four natatory. 

 The antenna- are simple. The body is narrow, elongated, and has 

 two long setaceous appendages at its posterior extremity . 



The third and last section DECEMPEDES, Lat. is composed of 

 Amphipoda, which present but six distinct feet. 



TYPHIS, Risso. 



But two very small antennae, the head large, and eyes not promi- 

 jient ; each pair of feet annexed to its peculiar segment, and the four 

 anterior terminated by a didactyle forceps. On each side of the 

 thorax are two moveable plates, forming a sort of lids or valves, 



See Encyclop. Method., article Pod 



f This and the following section, iu the first edition of the Rgne Animal, form 

 the second of the Isopoda, that of the Phytibranchiafa. But independently of our 

 having discovered mandibulnr palpi in some of these Crustacea, the form of the 

 subcaudal appendages appears to us to approximate them much nearer to the 

 Amphipoda than to the Isopoda. We may also observe that these animals, of 

 which we have seen but very few, have not yet been well studied. 



I According to the figure of Slabber Oniscus artnarins, Encyclop. Method., 

 Atl. d'Hist. Nat.,CCCXXX, 3, 4, the number of feet is but eight; reasoning 

 from analogy, I presume it to be fourteen ; besides, if the figure be exact, this genus 

 would belong to the next section. 



Enphnu liffioldft, Risso, Crust., Ill, 37; Desmar., Consid., 285 ; Apsevdts 

 1alpa, Leach ; Cancer yammanu talpa, Montag., Trans. Lin. Soc., IX, ir, 6 ; Des- 

 mar., Consid. : XLVI, 9. See the Gammanu hcteroclitus, Viviani, Phosphor. 

 Mans, II, ii, 12. 



N.B. The genus RHCEA, M. Edwards, Ann. des Sc. Nat. XIII. xiii, A, 292, dif- 

 fers from the preceding in the superior antenme, which are stouter, longer, and 



