152 Proceedings of the Royal Physical Society. 
D. acutipectus from a Fraterculine host. He also with B. Chapman (1899) 
introduced D. procax from a close ally of Uria grylle. All three species were 
secured on Pacific hosts. Of these species (to which fuller references are 
given below) we may take first Denny’s creations. His D. megacephalus 
and D. merguli, though neither was recorded for seventy years after their 
publication, are, I believe, perfectly valid and distinct species. 
As to D. platygaster, I am inclined to think that it does not belong to the 
group of Docophorus now under review. I had hoped it might turn out to be 
the species commonly found on Uria troile, but my examination of the types 
failed to bring this conviction. I speak with hesitation, as at the time of my 
visit the Denny collection was mounted on cards and not really in a condition 
for critical working. 
It is when one attempts to name material from Common Guillemot, 
razorbill and Puffin that difficulty may be felt. Three species in all infest 
these hosts. A study of the male genitalia made this beyond dispute. 
But it was only through the kindness of Professor Kellogg, who sent the 
writer a male and female of his D. calvus, that the identity of the three 
species could be made reasonably sure. What I believe to be D. acutipectus, 
Kell., is not hard to distinguish from D, celedoxus by a number of evident 
characters. But the differences between D. celedoxus and D. calvus are 
somewhat critical, and might easily be considered to be only of varietal 
value if one had not examined the genitalia. For this reason, although 
D. celedoxus occurs undoubtedly on U. troile, A. torda and F. aretica, it is 
so rare on the first named that records of the parasite from all three hosts 
should be received with reserve. So far as I am aware, the only recent 
European writer who has given expression to this feeling of hesitation is 
Eric Mjéberg (“Studien tiber Mallophagen und Anopluren,” Arkiv. for 
Zoologi, Band 6, No. 13, p. 182, 1910), who remarks under D. celedoxus, N.: 
“Von der Art liegen mir mehrere exemplare von sowohl Uria triole (sic), 
Uria grylle und Mormon arcticus vor (Mus. Gbg. Roth. Videll, cpse). Zwar 
stimmen die Ausgaben Piaget's nicht vollig mit den mir vorliegenden 
exemplaren ein; so ist Z. B, Clypeus nach vorn bei weitem nicht so tief 
ausgerandet und auch die Genitalflecke beim @ nicht voéllig ahnlich, ich 
fiihre sie aber zu dieser Art, der sie sich jedenfalls am_ niichsten 
anschliessen.” Mjéberg, from these remarks, appears to have had before 
him either D. celedowus and D. calvus, or D. celedoxus and D. megacephalus 
female—or possibly all three. 
To Messrs Bagnall and Hall belongs the credit of separating an 
unfamiliar Docophorus from among some examples of D. celedoxus collected 
on Puffin (Ff. arctica), Farne Islands, Northumberland (Jowrn. Leon. Biol., vol. 
