AMPHIPODA. 



223 



assert 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. Waders and different Fishes prey upon them. 

 For these interesting observations we are indebted to M. D'Or- 

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

 sponding member of that of Paris *. 

 The second section— Hetekopa, Lat.— is composed of those with 



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



for natation only. It comprises two subgenera |. 



Pterygocera, Latr. 



The thorax divided into several segments; four antennae furnished 

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

 and pinnated % ; 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 clayi- 

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

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

 The antennae 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- 

 nent ; 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 Podoch-e. 



t This and the following section, in the first edition of the Regne Animal, torm 

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

 having discovered mandibular 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. 



+ According to the figure of Slabber— 0«isciM arenarius, 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. 



§ Eupheus ligiouJes, Risso, Crust., Ill, 37 ; Desmar., Consid., 285 i— Apseudes 

 talpa, Leach ;— Cancer yammarus talpa, Montag., Trans. Lin. Soc, IX, iv, 6; Des- 

 mar., Consid.: XLVI, 9. See the Gummarus heteruclilus, Viviani, Phosphor. 

 Maris, II, ii, 12. ^ ^ ....„„ j-e 



N.B. The genus Rh(ea, M. Edwards, Ann. des So. Nat. XIII. xiu, A, 292, dif- 

 fers from the preceding la the superior antennae, which are stouter, longer, and 



