36 CARL BOVALLIUS, THE OXYCEPHALIDS. 



with a row of four or five stout spines, which are probably sensitive or- 

 gans of some kind (fig. 63). 



The metacarpus is usually narrow and linear; the hind margin 

 of the third and fourth pairs, and the front margin of the fifth, sixth, 

 and sometimes of the seventh is serrated or pectinated. In Xipho- 



cephalus the metacarpus of the fifth and sixth 

 pairs shows sensitive organs like those of the car- 

 pus mentioned just above (fig. 64). 



The dactylus of the first and second pairs as 

 well as that of some or of all the other pairs has 

 often a circular or ovate hole at the base of the 

 hind margin, in the case of the first four pairs, and 

 of the front margin in the case of the others. This 

 hole is an outlet for the secretion of the glands 

 Fi ' 65 c ^ ep}ialm which are present in many of the joints of the 

 peneopoda. Sometimes the hind margin is chanel- 



led, and in some few cases the apex of the dactylus is open (fig. 65). 

 The dactylus has often a tooth-like prominence in the middle of the 

 hind margin. 



9. The pleon and its appendages. 



The pleon differs less in form from that in the other Hyperids than 

 any of the other 'portions of the body. In Xiphocephalus it is much 

 elongated, longer than the perason (fig. 2); in Tullbergella it is very 

 broad and stout, the lower hind corners of the last segment projecting 

 into long sharp processes (fig. 74). In Stebbingella it is hard and 



tuberculous with grooves and ridges on 

 the external surface, in Dorycephalus 



_ the integument is thin and marked with 



Fig. 66. Oxycephu- Fig. 67. Simorhymh- peculiar pits and excavations. The pleo- 

 lus piscator. otus JMijeborgi. p O d a are nor mal; the peduncles are glo- 



bular, egg-shaped or almost cylindrical. On the inner side of the apex 

 of the peduncle are to be seen those peculiar organs first mentioned 

 by G. 0. SARS in his admirable work on the fresh-water Crustacea 

 of Norway 1 ) under the name epines pa rticuliers)) and termed coup- 



1) G. O. BARS. Crustaces d'eau douce cle la Norvge. I p. 5 and 133 pi. 

 5, fig. 8' and 8". Christiania 1869. 



