A NEW SPECIES OF PENTASTOMUM. 189 



Linguatula, "Corpus depressum." " Cavitas corporis in latera annulorum 

 porrecta, pectinata." 



Pentastomum, "Corpus teretiusculum. Cavitas corporis continua." 



It appears to me, however, that we see now sufficient anatomical distinc- 

 tions in the works of previous authors,* and in the research which has just been 

 recorded, to justify the elevation of these two groups to the position of distinct 

 genera. 



In the first group, for example, the hook-gland is diffuse, the oesophagus 

 opens into the anterior termination of the intestine, the testis is double, and the 

 vesicula seminalis single, while in the second group the hook-gland is collected 

 into two masses, one on either side of the intestine ; the oesophagus opens on 

 the inferior surface of the intestine, the testis is single, and in most cases the 

 vesicula seminalis seems to be double (P. oxycephalum would appear to be an 

 exception). 



It would seem only reasonable to suppose that such an amount of difference 

 in structure ought to be anatomically expressed by at least a generic difference ; 

 but further investigations into the anatomy of other members of the group 

 are very desirable to show whether they agree in the possession of these 

 characters. 



With respect to the names which these divisions should have, I do not 

 think it possible to improve upon those suggested by Leuckart. As van 

 i Beneden has pointed out,t Linguatula has a claim to recognition on the score 

 of priority, having been applied by Frohlich \ in the case of L. serrata. 



The two genera would then be diagnosed thus, the characters of the family 

 remaining as given by Leuckart : — 



Linguatula, Frohlich. 



(Type, Pentastomum tcenioides, Rudolphi. ) 



Body flattened i tody cavity sending out lateral processes into the annuli; hook- 

 gland diffuse ; opening of oesophagus into the extremity of the intestine ; testis 

 double ; vesicula seminalis single. 



Pentastomum, Rudolphi. 



(Type, P. proboscideum, Rudolphi.) 

 Body cylindrical ; body cavity even, without lateral prolongations ; a hook-gland 

 on either side of the intestine ; testis unpaired; vesicula seminalis single (?). 



* Van Beneden, Ann. Sci. Nat, s£r. 3 (Zool.) t. xi. p. 313, 1849; Diesing, Ann. des Wien. 

 \Mus., Bd. i. p. 1, 1836. 

 f Loc. cit., p. 314. 



t Frohlich, Naturforscher, Bd. xxiv. p. 148, 1789 (fide Diesing). 

 VOL. XXXII. PART I. 2 H 



