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 metacarpuf^ 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 dactylui' 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 



Fig. 65 Oxycephalus ^^i^jch are present in many of the joints of the 



perteopoda. 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 p/eon 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 peraeon (fig. 2); in Tullbergellu 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 

 peculiar pits and excavations. The pleo- 

 poda are normal; 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 

 oi Norway') under the name »épines particuliers» and termed »coup- 



Fig. 66. Oxycepha- Fig. 67. Simorhyncl 

 his piscator. otits Lilljeborgi. 



1) G. O. Sars. Crustacés d'eau douce de la Norvège. I p. 5 aud 133 pi. 

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



