250 DR JOHN RENNIE AND MR ALEXANDER REID ON 



The following additional points have been made out. 



The cuticula and sub-cuticula are well developed. Peripheral excretory canals are 

 numerous. The yolk follicles are very numerous and large. In longitudinal section 

 they appear as closely arranged, long, narrow bands, sometimes spindle-shaped, extending 

 from the sub-cuticula to the longitudinal muscle layer, which is well marked. 



The uterus has four or more turns, winding dorsally and ventrally in a spiral 

 manner (fig. 12). The shelled ova vary in size. A common dimension is: length 

 073 mm., breadth '051 mm. But there is a small proportion of long and narrow eggs 

 measuring '100 mm. by '041 mm. The eggs are operculate. 



The species appears to be unrecorded previously. No Dibothriocephalus species 

 have hitherto been described from either Arctic or Antarctic birds. It resembles 

 generally the scolex of D. quadratus in form and dimensions, but the proglottides are 

 smaller and the ova dimensions are dissimilar ; it resembles D, cordatus in the dimen- 

 sions of the eggs, but disagrees in other features. D. lanceolatus is a much smaller 

 form. In general features D. pygoscelis resembles D. romeri, but is on the whole 

 larger, and again the egg dimensions are greater. In particular, the specially large 

 size of the shelled ova and form of the scolex differentiate it from all other described 

 Arctic or Antarctic species occurring in either birds or Pinnipedia. 



We propose to name it Dibothriocephalus pygoscelis. 



Sub-family PLEUROGONIN/E (Ariola). 

 Genus Anchistrocephalus, Monticelli, 1 890. 



SYNONYMS. 



Txnia, Auctorum. 

 Bothrioeeplialus, Rudolphi, 1808. 

 Diboihrium, Diesing, 1850. 

 Polyonchobothriwn, Diesing, 1850. 

 Anchistrocephalus, Monticelli, 1890. 



Anchistrocephalus microcephalus (Rud.), 1819. (PI. I. fig. 3.) 



This tapeworm was found in very large numbers in the intestine of the Sunfish, 

 Orthagoriscus mola, in a mass weighing several pounds, and almost completely 

 blocking the intestine. O. mola was captured at Station 107. 



It was first described by RUDOLPHI, in 1810, and its occurrence has since been 

 noted and its anatomy described by other investigators. It is a readily recognisable 

 species, and does not appear to have been recorded in any host other than the Sunfish. 

 The scolex has a pair of rather deep, open, thick-margined, square-looking suckers 

 topped by a hemispherical rostellum, the base of which is encircled by several close- 

 set rows of small hooks (fig. 3 (a)). 



The genital pores are marginal in position (fig. 3 (6)). 



(ROY. soc. EDIN. TRANS., VOL. XLVIIL, 448.) 



