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Mr. L. Harrison on 



Emeus also to have been derived, though the evidence here 

 is not quite so convincing. 



So much for the few suggestions I have already put 

 forward in print. As I have said already, much more will 

 have to be known about the Mallophaga themselves before 

 any general results can be adduced. But the following 

 attempt will serve to illustrate both my ideas and their 

 possibilities. 



The genus Lipeurus contains a great number of species 

 found upon nearly all bird families. The Lipeuri of Petrels 

 exhibit a very distinct facies, with the details of which I 

 need not trouble you, but which renders them easily recog- 

 nisable at a glance as Petrel parasites. They fall into six 

 well-marked groups, which may easily be distinguished by 

 the structure of the head. These six groups I name after the 

 best-known species in each of them, the clypeatus, pelagicus, 

 diversus, fuliffinosus, gurlti, and mutabilis groups, but, for 

 our present purpose, it will suffice to distinguish them by 

 the first six letters of the alphabet. The precise inter-relation 

 of these groups is not quite certain. I express it tentatively 

 in the diagram. 



B. palaglcue groupj 



Text-figure 5. 



A clypeatus group 



F. mutablllo group. 

 I. gurlti group 



D. fxaiglnoBue group 

 C. dlvarBue group. 



The main things that stand out are the distinctness of 

 groups E and F from the remaining four, though they show 

 indications of derivation from the clypeatus (A) type. 

 Group A is also distinct ; groups B and C fairly close 



