166 Mr. C. Spence Bate on the Nidification of Crustacea. 



that fully warrant the classification of Amphitoe, Sunamphitoe, 

 Podocerus, Cerapus, and Siphonocetus into a subfamily. 



The most important parts by which classification can be carried 

 out are the appendages at each extremity, — the antcnnre and 

 the posterior pleopoda. The gnathopoda also are important; 

 but they frequently differ in the sexes, and a great variety in 

 their formation is compatible with the integrity of a genus. 



Fig. 



3. 



4. 



Amphitoe. 



Sunamphitoi!. 



Podocerus. 



Cerapus. 



Siphonocetus. 



In Amphitoe the upper antenna has no complementary append- 

 age; in the lower antenna, the flagellum (fig. 1 c) terminates 

 simply ; the posterior pleopod (fig. 1 a) is double-branched, one 

 branch being furnished with two or more short, stout spines 

 planted in such a position as to be directed forwards and serve 

 the purpose of hooks ; the other is developed in the form of a 

 scale or plate, more or less fringed with fine hairs. The telson 

 (fig. 1 i) is a simple plate narrowing posteriorly to an apex. 



The genus Sunamjjhitoe is very near to that of AmpJntoe, the 

 great diff'erence being that the telson of Sunamphitoe is developed 

 into a single well- formed and powerful hook (fig. 2h). 



In Podocerus the upper antenna has a rudimentary secondary 

 appendage (fig. 3^). The flagellum of the lower antenna (c) 

 consists of only a few articulations, and the last two are fur- 

 nished with two or more short, stout, curved, hook-like spines, 

 and a few strong hairs. The posterior pleopod (fig. 3 a) is double- 

 branched; the outer branch with two or more hook-like spines. 



