206 ENTOZOA. 



obtusely rounded in front, and produced behind, so as to form a 

 conspicuous, tail-like appendage. At the anterior and ventral 

 aspect of the head there are six small orbicular pores, serially dis- 

 posed in a semilunar form, and there is also a sucker-hke organ 

 situated in the central Hne about the root of the tail. A small 

 opening is described as existing at the caudal extremity. Van 

 Beneden and Gervais have supposed that this parasite may, after 

 all, turn out to be the well-known Pentastoma denticulatum. This 

 view, however, is quite inadmissible, as one may perceive from a 

 consideration of the size, shape, want of claws, and, more especially, 

 from the presence of a ventral acetabulum in Hexathyridium. 



9. Hexathyridium yenabum. 



H. venarum, Treutler; Jordens; Rudolphi; etc. 



Hexastoma venarum, Ouvier. 



Hexacotyle venarum, BlainviUe. 



Linguatula venarum, Lamarck. 



Polystoma sanguicola, DeUe Chiaje ; Frick. 



P. venarum, Zeder ; Rudolphi ; Dujardin ; Owen; etc. 



This species is better known than the above. Treutler origi- 

 nally obtained two specimens from the blood of the anterior tibial 

 vein of a young man who accidentally ruptured the vessel while bath- 

 ing, at Leipsic. Rudolphi and others sought to throw doubt on 

 Treutler' s observation, and referred these worms to the fresh- 

 water Planarice. At Naples, however, Delle Chiaje subsequently 

 procured specimens from the sputa of two young persons suffering 

 from hgemoptysis ; and a fourth instance also appears to have been 

 noticed by FoUina, where the worm occured in venous blood. This 

 species attains a length of three hnes, is cyhndrico-lanceolate in 

 shape, its six suckers being biserially disposed on the under side 

 of the so-called head. Davaine in his " Traite," previously quoted, 

 gives Treutler's original description at ftiU length ; but, notwith- 



