M. V. Lebour 
447 
head, and this head bear a row of fine spines arranged as far as I 
can make out as a crown undulating on the ventral surface, straight 
dorsally. The oral sucker has papillae arranged round its opening and 
there are also papillae round the oral sucker. Oral sucker 0 06 mm. 
across, short prepharynx, small but muscular pharynx. Oesophagus 
long, reaching to about the centre of the body where it bifurcates, 
intestinal caeca reaching nearly to the posterior end of the body. 
Ventral sucker 0099 mm. across but with the space round it may 
appear much larger and it is difficult to define its limits. Excretory 
vesicle round receiving two thick lateral canals. 
Here we have a very characteristic and common form but nothing 
further is known of its life-history. It almost certainly inhabits a bird 
in its adult state. 
It is interesting to note that full-grown cercariae were found in the 
mantle cavity of Purpura together with the very young rediae, which 
seems to indicate that the cercaria emerges from its host by the same 
route that the redia uses to get to the digestive gland. 
Cercaria patellae sp. inq. 
(Lebour, 1907 B, p. 103.) 
(PI. XXIX, figs. 4, 5.) 
This cercaria occurred once in the digestive gland of Patella vulgata 
from Loch Ryan out of 16 examined in September. The gonad was 
completely destroyed. 
Redia colourless, long and transparent, I'S mm. or more in length. 
Pharynx conspicuous but no intestine could be seen. All the rediae 
were full of tailed cercariae. 
The cercaria measures 0'50 mm. in length with the tail thin and 
measuring less than half the length of the body and abruptly truncated. 
Body covered with small spines. Head surrounded by two complete 
rows of longer spines. Oral sucker leads to a narrow prephaiynx, 
muscular pharynx, long oesophagus branching into caeca reaching 
nearly to the posterior end of the body. Ventral sucker behind the 
centre of the body. Excretory vesicle receiving two unbranched latei’al 
canals full of bright granules. 
Nothing further is known of the life-history. 
I had thought it was possibly a Stepha^wchasmus but it is very 
probably, as suggested to me by Dr Nicoll, that it is the cercaria of 
Echinostephilla virgula which I have described from the turnstone 
(1909, p. 3). 
