30 



CARL BOVALLIUS, THE OXYCEPHALIDS. 



like, bent inwards against the tip of the mandibles. The margins of the 

 lateral laminae are often tuberculated and serrated or sparingly set with 

 short bristles or fine hairs. 



8. The perceon and its appendages. 



According to the varying form of body in the different genera 

 the perseon is short and stout, as in Tnllbergella (fig. 1), or long and 

 almost rod-like, as in Xiphocephalus (fig. 2), but it may be obser- 

 ved that in the enormous elongation which occurs for instance in 

 Xiphocephalus, has the perseon comparatively less share than the 

 head, the urus, and the pleon. 



Fig. 46. The first and second peraeonal seg- 

 ments of Xiphocephalus Whitei. c? 



Fig. 47. Th.e sixth and seventh personal seg- 

 ments of Xiphocephalus Whitei. <5- 



The epimerals are distinct in all the genera of the Oxycepha- 

 lidae (fig. 1, 3, 4, 5 and 27}, but in the Xiphocephalidee only the 

 epimeral of the first pair of perseopoda is distinct, the others being coa- 

 lesced with the corresponding segments (fig. 46 and 47). 



The branchial vesicles are attached to the second and four 

 following pairs of pereeopoda in all species of both families. Those in 

 the Oxycephalidee are comparatively small, while those in the Xipho- 

 cephalidas are very large (fig. 46 and 47). 



The ovitectrices vary in form in the different genera of the 

 Oxycephalidae; in Tullbergella, Simorhynchotus, and Stebbing- 

 ella they are broadly ovate, in Dorycephalus, Streetsia, Oxyce- 

 phalus, and Leptocotis they are more elongated, the margins being 

 smooth without hairs, and in Glossocephalus they are more irregular 

 in form, the lower end being produced into a sharp angle. 



