Mr. C. Spence Bate on the Nidification of Cy'ustacea, 167 



tlie inner more styliform than in Amphitoe, and tipped with one 

 or more short spines. The telson (fig. 3 b) is simple and pointed 

 as in Amphitoe. 



In Cerapus the upper antenna has a very rudimentary second- 

 ary appendage (fig. 4 c?). The lower antenna has a simple 

 flagellum {c). The posterior pleopod [a) is single-branched, 

 and terminates in two imperfect hooks. The telson [b] is double- 

 lobed, each lobe being covered with a number of short points 

 directed anteriorly. 



In Siphonocetus the upper antenna is without any secondary 

 appendage ; the lower has the flagellum reduced to two or three 

 stout articulations (fig. 5 c). The posterior pleopod {a) is 

 single-branched, the terminal joint being very short, and fur- 

 nished with two well-formed, powerful hooks. The telson {b) is 

 single (?)-lobed, and furnished with a number of short points 

 directed anteriorly. 



If we compare the relative parts, we find that the upper an- 

 tennae of Amphitoe^ Sunamphitoe, and Siphonocetus are without 

 secondary appendages; while those of Podocerus and Cerapus 

 have them in rudimentary (microscopic) forms. The lower an- 

 tennae of Amphitoe, Sunamphitoe, and Cerapus alike possess 

 simple flagella ; while those of Podocerus and Siphonocetus have 

 the flagella reduced to two or three strong articulations furnished 

 with stout hairs, some of which in Podocerus are reduced to 

 short, curved spines. The posterior pleopod scarcely difi*ers in 

 Amphitoe, Sunamphitoe, and Podocerus; and in Cerapus it difi*ers 

 from Siphonocetus in the absence of the squamiform branch. 

 The telson in Amphitoe resembles that of Podocerus, while the 

 telson of Cerapus^ diff^ers from that of Siphonocetus in the former 

 being double- and the latter being single-lobed ; whereas the 

 telson of Sunamphitoe is peculiar to itself. 



The hairs with which many of these Crustacea are furnished 

 evidently constitute a peculiar feature in this small group. 

 Losing their soft and pliant form, they assume that of short 

 points, strong spinous processes, and curved hooks. These 

 changes are brought about to serve some efficient purpose in the 

 oeconomy of the animals. The hooks are placed on the posterior 

 appendages of the several genera, and are so directed that the 

 animals can pull themselves backwards; and when they are 



* There can be little doubt that Erichthoneus of Edwards is synony- 

 mous with Cerapus of Say, and, according to Dana's figures, the genus 

 Pyctilus also. The female of Cerapus bears a much nearer resemblance to 

 Podocerus than to its male, — a circumstance that had led me to describe a 

 female Cerapus, in the * Synopsis of the British Edriophthalma,' as Podo- 

 cerus punctatus (having never seen the male) ; it agrees closely with 

 Leach's specimen of Jassa punctata in the British Museum. 



