500 Dr. H. A. Baylis on 
v. Linstow (1884) regards Ascaris semiteres as a synonym 
of A. ensicaudata, and gives an extensive list of hosts for 
this species in consequence. His figures (1884) seem to 
have been based on material really belonging to P. semiteres. 
An examination of material from Vanellus vanellus, Turdus 
merula and Sturnus vulgaris shows that it includes two forms 
which, while possibly hardly more than subspecies, are never- 
theless quite distinct and recognizable. 
P. semiteres (Zeder, 1800), from Vanellus, differs from the 
rest of the material (P. ensicaudatum) in (1) the presence of 
Porrocecum semiteres. Dorsal lip, external aspect. 
d.r., dentigerous ridge; ¢., interlabium ; p., papilla. 
conspicuous lateral cervical ale; (2) the much better deve- 
loped condition of the intestinal caecum (see figs. 5, 6); (3) the 
much greater size of the lips in mature specimens (see 
figs. 3, A) ; and (4) the length of the spicules of the male, 
those of P. semiteres measuring 0°77-0°8 mm., while those of 
P. ensicaudatum measure only 0°62-0°63 mm. 
The shape of the pulp of the dorsal lip (figs. 3, 4) is very 
similar in the two forms. Hach of the two main a ace 
lobes has an indentation in its outline, and sends out a 
outwardly and backwardly directed “horn.” In both cases 
