188 MR W. E. HOYLE ON 



rounded nucleated cells about two deep, and having a diameter of some 

 0-007 mm. 



Systematic Position. 



The parasite which has just been described finds its nearest congener in 

 Pentastomum polyzonum, Harley."" It is distinguished from it, however, by 

 the number of segments, which in the females under consideration amounts to 

 18-22, whilst in the adult females of P. polyzonum hitherto described t it does 

 not exceed 19, and it is very unlikely that an immature form should have more, 

 though it would very probably have fewer segments than the adult. In this 

 case the difference in size is of course valueless as a specific character. 



I propose therefore to make the specimens above described the type of a 

 new species, whose diagnosis would be provisionally as follows : — 



Pentastomum protelis, n. sp. 



Body cylindrical in the anterior half, slightly tapering posteriorly, terminal 

 segment obtusely pointed. No clear distinction between cephalolhorax and 

 abdomen. Head hemispheroidal, equal in diameter to the body. Mouth fur- 

 nished ivith a papilla, perhaps a protrusible proboscis. No accessory hooks. 

 Stigmata arranged in numerous irregular roivs on all the segments. Male, 

 13-17 mm. in length, with 16 or 17 annuli. Female, 20-25 mm. in length, with 

 18-22 annuli. Habitat, the mesentery of Proteles cristatus, enclosed in a con- 

 nective tissue cyst. 



It is, of course, possible that some future investigator will demonstrate the 

 identity of this form with an early stage of P. polyzonum, and this possibility 

 is increased by the fact that specimens of this species were found in an 

 African serpent,^ of which part of the globe Proteles cristatus is also an 

 inhabitant. 



If such should be the case, Leuckakt's opinion that P. Diesingii, v. Ben., is 

 the immature forni of this would be untenable, for this form exhibits distinc- 

 tions in its body form, oral papilla, and muscular system, sufficient to prove 

 its specific distinctness from the subject of this paper. 



I propose now to make a few concluding observations on the subdivision of 

 the family Pentastomidre. 



In the brief systematic portion of Leuckakt's § work, the species are grouped 

 under two headings, which are regarded as being of sub-generic value — 



* Proe. Zool. Soc. Lond., part 25, p. 115, 1857. 



t B' ' i.. Ann. <nt<l Mag. Nat. Hist., ser. 5, vol. vi p. 176, 1880. 



X BbMi Im eit. p. 173. § Luc. eit, p. 152. 



