208 CRUSTACEA. 



SYSMATA, JRisso : ante MELICERTA, ejusd. 



Whore the second pair of claws are larger than the first *, and 



ATHANAS, Leach. 



In which, on the contrary, the first pair is larger than the second f . 

 The last subgenus of this section, that of 



PASipRflEA, Sav., 



Although closely approximated to several of the preceding by the 

 superior antennae which are terminated by two threads, by the form 

 of the four anterior feet, terminating in a didactyle forceps, and pre- 

 ceded by a joint, without annular divisions, and by the shortness of 

 the rostrum, differs from them in several respects. A testaceous ap- 

 pendage is very evident at the external base of their feet; these latter, 

 with the exception of the claws, which are larger and nearly equal, 

 are very slender and filiform ; the body is greatly elongated, strongly 

 compressed, and extremely soft. 



Pas.sivado; Alpheus sivado, Risso, Crust., 111,2; Desmar., 

 Consid., p. 240, is two inches and a half long, and four lines and 

 a half in breadth. The body is transparent, of a nacre white 

 edged with red, the caudal fin marked with small dots of the same 

 colour. The rostrum is sharp and slightly curved at the point. 

 Claws reddish. 



It is very abundant on the shores of Nice, and according to 

 Risso spawns in June and July. No other species has yet been 

 observed. 



Our fifth and last section of the Macroura, that of the SCHIZOPODA, 

 appears to connect the Macroura with the following order. The 

 feet, none of which terminates in a forceps, are very slender, resem- 

 ble thongs, are furnished with an appendage more or less long, 

 arising from their external side near their base, and serving for 

 natation only. The ova are situated between them, and not under 

 the tail. The ocular pedicles are very short. As in most of the 

 Macroura the front projects into a point or rostrum. The shell is thin, 

 and the tail terminates, as usual, in a sort of fin. They are small, 

 and inhabit salt water. 



Here the eyes are very apparent ; the lateral antennae are accom- 

 panied by a scale, and the intermediaries terminated by two threads 

 and composed of several small segments, as in the preceding genera. 



MYSIS, Latr., 



Antennse and feet exposed ; the shell elongated ; nearly square or 

 cylindrical ; the eyes closely approximated, and the feet capillary, as 

 if formed of two threads J. 



* Li/smuta selicauda, Risso, Cnist., II, 1 ; Desmar., Consid., p. 238. 



f Athanus nitescens, Leach, Malac. Brit., XL1V ; Desmar., Consid., p. 239, 240 ; 

 de Brfli., Crust., du Calv., p. 23, 24. 



I Mi/sis Fabricii, Leach ; Encyc. Method., All. d'Hist. Nat., CCCXXXVI, 8, 9 ; 

 Cancer ontlatus, Oth. ; Fab., Groe.nl., fig. 1. See Depmar., Consid., p. 241, 242. 



