E. LÖNNBERG, ON THE RHAMPHOTHECA OF BIRDS. 507 



these birds. The rhamphotheca of a Tern stånds when com- 

 pared with that of a Grull or Skua as an analogy to the bill 

 of the Anhinga compared with that of a Cormorant. 



The structure of the bilis of Limicolce may be derived 

 from such a one as that found in Lari. Eor the habits and 

 the diet of most Limicolce it is only necessary that the extreme 

 tips of upper and lower jaws are covered by härd and horny 

 pieces. Bostrale and mentale are therefore as a rnle developed 

 as such; bnt to increase the sensibility of the bill, which for 

 a great many members of this group is of importance for 

 the method in which they procure their food, the horny 

 structures of the labial and infralabial elements are often 

 reduced and substituted by a soft skin rich in sensory organs. 

 In many others, however, these plates, as well, retain their 

 original horny nature. In either case the .same parts may, 

 as a rule quite easily, be distinguished in the bill of the 

 members of Charadriidce as in that of Laridce. A longitudinal 

 nasal groove on either side of the upper rhamphotheca divides 

 the internasal and labial elements. A similar groove on 

 either side indicates the boundary line between the infralabial 

 and the submandibular, which in the same way as in the 

 Lari lie one a bo ve the other. These are the chief features 

 but according to the different habits, diet etc. of these birds 

 the shape and structure of the bill is greatly transformed 

 to suit the needs of life. The different elements, mentioned 

 above, are, however, just as well present in the short and 

 firm beak of the Lapwings as in the long and basally soft 

 pinchers of Limosa. In the former, however, rostrale is better 

 developed and defined from the internasal tract. The fact 

 that in all members of Charadriidce, even in such in which 

 the bill is modified as in Becurvirostra, the different ele- 

 ments may be recognized, as stated above, is well worth of 

 notice. 



The external structure of the bill when fully understood 

 may therefore also be used as a distinguishing feature in classi- 

 fying. For instance in a case such as follows. The Ibis and 

 the Curlew (Numenius) have both acquired a long, curved bill 

 of similar shape and this gives a certain likeness in the outer 

 appearance of those else widely different birds. Now only 

 an examination of the lower rhamphotheca is sufficient to 

 reveal the fundamental difference between these birds, as the 



