162 CALIFORNIA ACADEMY OF SCIENCES. 



species, although in three genera they are absent in a 

 few cases. On the other hand, in the Amblycera they 

 are absent in all but two genera, and of these one has 

 them present in all species, but in the other they may 

 be present or may be absent. Of thirty-eight species 

 of Docophorus, twenty-six species of Ljpeurus, and 

 twenty-nine species of Nirrnus examined — all that 

 were accessible — only in Docophorus icterodes, Lipeurus 

 'picturatus, L. longipilus, and Nirmus signatus are the 

 structures absent. From this it is evident that the ex- 

 ceptions to the occurrence of the oesophageal sclerite and 

 glands in North American Ischnocera are few. It is 

 worthy of notice also that the species of this suborder 

 lacking them occur in the three largest genera, — the 

 species of Docophorus, Lipeurus, and Nirmus being far 

 more numerous than those of all the other genera of 

 the same suborder together. 



The following genera have been found so far only on 

 European birds, Akidoprocius, Boopia, Bothrioinetopus , 

 Eureum, and Ornithobius. Taschenberg (1882) and Pia- 

 get (1880), however, give good figures of all these gen- 

 era, and in their figures the presence or absence of the 

 sclerite is apparently intended to be shown, although 

 whether it is or is not present is not stated in the 

 description of each species. The figures can probably 

 be relied on to show at least in what species it is pres- 

 ent. According to them the structure is present only 

 in Akidoprocius. This genus and also Bothriomelopus 

 and Ornithobius belong to the Ischnocera, so that it 

 appears that there are two genera of this suborder in 

 which the sclerite is absent; but this is without proof. 

 If it is absent in the two Amblyceran genera, Boopia 

 and Eureum, they agree with most of the other forms 

 of their suborder. The sclerite appears to be absent 



