1892.] OF THE GENUS PERICH.ETA. 169 



In b there are three pairs uf spermathecae in segments vi., vii., and 

 viii., which are in every respect perfectly normal. 



In c there are two pairs lying in vi. and vii., but quite normal ia 

 structure. 



It mav be that I am wrong in associating all these individuals 

 together under one specific name. 



Perich^ta hesperidum, n. sp. 



Two individuals out of the five specimens just referred to, of which 

 I have described three under the name, of Perichceta barbadensis, 

 presented certain differences ; these differences would, if the speci- 

 mens had come from a diiFerent locality, be undoubtedly considered 

 of specific value. As it is, I am uncertain, considering their ex- 

 ceedingly close similarity in coloration, whetlier to regard all five 

 individuals as belonging to one prottan species, or whether to regard 

 the two specimens described here as a distinct species. Since the 

 differences which they show to the three described as Perichceta 

 barbadensis are more marked than either of the three exhibit among 

 themselves, I give them at least a provisional name. 



The external characters are those of Perichceta barbadensis, ex- 

 cepting that there are no setce ypon (he clitellum and that there are no 

 genital j)opillcB. In describing the last species, I pointed out that 

 tliere is a gradual reduction in the three specimens of the setfe upon 

 the clitellum, which is accompanied by a reduction in the genital 

 papillae. In the two specimens which I describe here as Perichceta 

 hesperidum this reduction in number has culminated in the total 

 disappearance of both the clitellar setae and the genital papillae. 

 If it were not for certain differences in the internal anatomy, to which 

 I shall call attention later, these facts would rather show that there 

 is no necessity for separating the forms specifically. 



In the internal anatomy there are, however, differences. I should 

 say, however, that I have only dissected one of the two individuals 

 associated together here under the name of Perichceta hesperidum. 



In that worm the cceca are remarkably small as compared with 

 those of other species. The intestine is provided with a fairly 

 well-marked typhlosole ; it commences in the xvth segment. 



There are two pairs oi spermathecce, v:h\c\\ lie in segments \'\i, 

 and viii. and open on the border-line between segments vii./viii. and 

 viii./ix. ; in the case of the anterior pair, the displacement of mesentery 

 makes the apertures, when viewed from the inside of the body, look 

 as if they were placed in the middle of segment vii. 



The diverticulum is contorted. 



I only found a single pair of receptacula ovorum in place of the 

 two pairs of the last species ; they are attached to the front wall of 

 segment xiii. and lie above the ovaries ; they are elongate and lie 

 obliquely on the septum. 



The atrium shows a difference of importance from the last species ; 

 this is the presence of a terminal sac. This sac is, however, so 

 extremely small in the present species that it needs careful looking 



Proc. Zool. Soc— 1892, No. XII. 12 



