REPORT ON THE CRUSTACEA MACRURA. 691 



The second pair of gnathopoda (fig. li) is long, slender, and pediform, longer than 

 any of the pereiopoda, which it resembles in the number of the articulations, but differs in 

 having the meros and propodos longer and the carpos and dactylos shorter. 



The first pair of pereiopoda (fig. 1/:) is monodactyle, and has the carpos and 

 propodos subequal and the dactylos short. The second pair (fig. ll) is more robust 

 than the first, and chelate. The third (fig. lm), fourth, and fifth pairs are rather more 

 slender than the second, subequal in length, and terminate in a sharp and longer 

 dactylos. 



Family Atyidj;. 



Carapace dorsally smooth, rounded, and anteriorly produced to a flattened rostrum. 

 Pleon short and robust. First antennae having a stylocerite. Second carrying a short 

 scaphocerite. Mandibles having a molar process and psalistoma but no synaphipod. 

 Second pair of gnathopoda four -jointed and pediform. First and second pairs of 

 pereiopoda chelate, dactylos and pollex spatuliform or spoon-shaped. Third, fourth, 

 and fifth pairs simple. Pleopoda biramose. Rhipidura well developed. Telson 

 flattened, truncate. 



Atya, Leach. 



Atys, Leach, Trans. Linn. Soc. Lond., vol. xi. p. 345, 1815. 

 Atya, Leach, Zool. Miscell., vol. viii. p. 29, 1817. 



,, Latreille, Begne Anim. de Cuvier, torn. iv. p. 93. 



,, Desmarest, Consid. sur les Crust., p. 215. 



,, Roux, Mem. class, crust. Salicoques, p. 27; FeVussae, Bull. Sci. Nat., torn. xxvii., 1831. 



,, Wiegmann, "Wiegmann's Archiv f. Naturgesch., Jahrg. iii. p. 145, 1836. 



,, Milne-Edwards, Hist. Nat. Crust., torn. ii. p. 347, 1837. 



„ Newport, Ann. and Mag. Nat. Hist., vol. xix. p. 158, 1847. 



„ A. Milne-Edwards, Ann. Soc. Entom. France, torn. iv. p. 145, 1864. 

 Atyoida, Randall, Journ. Acad. Nat. Sci. Philad., vol. viii. p. 140. <b 



Animal laterally compressed, dorsally smooth. Frontal margin produced to a 

 rostrum in line with the carapace, not laterally compressed. 



First and second pairs of pereiopoda short and chelate ; chela? fringed with long 

 hairs. Third pair large and long ; fourth and fifth robust and shorter than the third. 



Pleopoda short, broad, and foliaceous. 



Rhipidura short, robust, and well developed. 



The carapace is quite one-third the length of the animal, and in some species more. 

 The dorsal surface projects to a rostrum and is anteriorly depressed in the same 

 continuous line ; it is flat and broad at the base and tapers to the apex. 



