222 BARKER. 



as "a long cylindrical structure, extending from the genital pore 

 around the dorsal side of the acetabulum to the vicinity of the ovary 

 and the shell-gland, and in some cases to the anterior border of the 

 testes." According to Linton (1910, p. 25) the cirrus pouch in P. 

 ovalis (PI. II, Fig. 10) is "relatively short, reaching barely to the 

 posterior edge of the acetabulum." Both Linton and Pratt consider 

 the differences in the extent of the cirrus pouch, together with other 

 minor differences, to be of specific rank. It is evident that the form 

 which we have described resembles P. omlis Linton more than it does 

 P. tertins Pratt or P. irrorahis (R.) Looss; but it differs from P. ovalis 

 Linton in minor characters and distinctively in the position and 

 lesser extent of the cirrus pouch. The difference in the lerigth of the 

 cirrus pouch in P. ovalis Linton and in the trematode here described 

 is greater than that between P. ovalis and P. tcrtius Pratt and decidedly 

 greater than that between P. tcrtius Pratt and P. irroratus (R.) Looss. 

 We agree with Pratt that the "actual position is undoubtedly de- 

 pendent upon the condition of contraction," but it seems improbable 

 that this constant and marked difference could be due entirely to the 

 contraction of the acetabulum or the body. 



We feel warranted in ascribing to this difference in the position and 

 extent of the cirrus pouch, taken together with the minor differences 

 noted, a specific value, and therefore class this trematode as a new 

 species in the'genus P achy psoitis, designating it as Pachypsolus hrachus} 



In the four species of Pachypsolus now recorded we find, in addition 

 to differences of secondary importance, a striking gradation in the 

 position and size of the cirrus pouch, which is the distinctive specific 

 character. The old question, raised by Looss, arises as to specific 

 differences and the specific effects of different hosts on the same 

 species. 



From the standpoint of geographical distribution, it is of interest to 

 find in the Hawk's-bill Turtle from the Bermudas a different species 

 of Pachypsohis from that found in the Loggerhead Turtles of New 

 Guinea and the Mediterranean and from those found in the Logger- 

 head Turtles of the Tortugas. 



1 i3paxvs, short, having reference to the cirrus pouch. 



