Mr. C. Spcncc Bate on the Nidificatiun of Crustacea. 167 



the inner more styliforin than in Amphito'e, and tipped with one 

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

 as in Amphito'e. 



In Cerapus the upper antenna has a very rudimentary second- 

 ary appendage (fig. 4</). The lower antenna has a simple 

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

 and terminates in two imperlcct 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 lias the flagcllam 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 Amphito'e, Sunamph'ito'e, and Siphonocetus are without 

 secondary appendages ; while those of Podocerus and Cerapus 

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

 tenuce of Amphito'e, SunampJiito'e, 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 w^hich in Podocerus are reduced to 

 short, curved spines. The posterior pleopod scarcely differs in 

 Amphito'e, Sunamphito'e, and Podocerus; and in Cerapus it differs 

 from Siphonocetus in the absence of the squamiform branch. 

 The telson in Amphito'e resembles that of Podocerus, while the 

 telson of Cerapus* differs from that of Siphonocetus ii\ the former 

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

 telson of Sunamphito'e 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 

 Pyct'dus 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 Jasta punctata in the British Museum. 



