TWO NEW BRITISH NEMERTEANS. 559 



both dorso-veiitrally nnd in an antero-posterior direction 

 (fig. 19, b — e, and fig-. 20). It is not embraced by a blood 

 lacuna. The epithelium of the ciliated canal (as is usual 

 among the Ueteronemerteans) contains specialised large cells 

 externally, seven in number, as seen in transverse section. 

 The ciliated canal arises dorso-laterally from the ciliated 

 circular ring surrounding the head just in front of the mouth. 



Neither eyes nor frontal organ are present. 



The head glands are largely developed, as in Eupolia. 

 They reach backwards dorsally, and to a less extent ventrally 

 past the brain, lying in the outer longitudinal muscle layer. 

 Their substance stains deeply with thionin. 



At the time when Burger's monograph was published the 

 Eupoliidas contained but three genera, viz. Eupolia, 

 Valenciuia, and Pol i ops is. Since then three other 

 genera (including the present one) have been added, viz. 

 Parapolia (Coe [4]), Zygeupolia (Thompson [7j), and 

 Oxypolia; consequently I have thought it advisable to add 

 a table showing the main differences presented by the six 

 genera which now form the family. 



From this table it will be seen that Oxypolia holds a 

 position more or less internietliate between Valenciuia and 

 Eupolia. It is more closely related to the former genus, 

 though, in addition to characters given above, it may be dis- 

 tinguished by the following : 



(1) The body is shorter and stouter. in build than in Va- 

 lenciuia. Moreover in Oxypolia the posterior portion is 

 not thicker than the anterior. 



(2) There is no circular ciliated head furrow in Valen- 

 ciuia. 



(o) Whilst the head glands in Oxypolia exactly resemble 

 those of Eupolia, those of Valenciuia, according to 

 Biirger (5, p. 186), are slighter in build, recalling those of 

 many Lineidae. 



(4) The cephalic vascular lacunae in Valenciuia form a 

 broken ring anteriorly (2, pi. ii, fig. 53). In Oxypolia 

 they are quite horizontal as in Eupolia. 



