— 242 — 



different forms belonginp to this species diHer very much, but 

 agree in this respect, that it is extremely difficult to determine 

 the various forms. 



Neumann asks the question as to whether there are 

 probably two simihir species occurring together: nnjstacea and 

 murina, as H e u g 1 i n presumes is the case in Nord-east Africa 

 (Journ. f. Orn., 1906, p. 277). Zedlitz does not consider it 

 probable that one darker, larger form and another lighter, 

 smaller form occur together, but combines these two into one 

 common form. He suminarizes his investigation under three 

 heads: 1. cfcT and 99 ^^ "ot differ essentially in measurements; 

 2 dark and light sjjecimens are found of both sexes; 3. the 

 breast-patch, as a rule, is not found in 9^ do^ always in cf. 

 These results are — as far as I can find — quite correct and 

 in the sories of 20 sj)ecimens I have before nie there is every 

 possible, both gieat and little, individual variation represented. 



S c 1 a t e r and M. - P r a e d (Ibis, 1918, p 676—677) were 

 however the first to deal exhaustively with the different forms 

 of mystacea and they have separated four. 



According to these writers the form occuring in East Africa 

 and Uganda is named P. mystacea tenella Cab., which is larger 

 than — otherwise very similar to — melanorhyncha from West 

 Africa. The wing-measurement for tenella is 48 — 55 mm. 



V. Someren has, however, described a new form: immu- 

 tabilis, which differs from tenella (which is a coastal bird) in 

 being "considerably larger and much darker. Further, it lacks 

 the wide white supercilium found in tenella. Wings 53 — 57 mm. 

 It ranges from Ukamba in East Africa to Uganda (not including 

 the S. Ankola River destrict)". 



If the wing-measurement of tenella amounts to 55 mm. and 

 the maximum for immutahilis is 57 mm. then the difference is 

 by no means "considerable", and specimens of both forms reaching 

 55 mm. or less must then be distinguished by means of the other 

 distinctive features. With reference to the lack of the wide 

 supercilium in immutahilis, and even if he had not done so, we 

 should of course, judging from the locality from which they ori- 

 ginate, refer these individuals to the above-mentioned form. Only 

 2 cf specimens attain the maximum for the wing of tenella^ all 

 the others fall short, as appears from the following table: 



Wing, tarsus, 



50 mm. 20 mm. cf Ngong. 



51, 51, 52.5 mm 21 — 22 mm cTcT Kiambu. 



54 mm. 21 5 mm. cf Naiwasha. 



51, 53, 54, 54, 54, 54, 55, 55 mm. 21—22 mm. cTcT Elgou. 



53 mm. 20 mm. cf Eldoret. 



50, 51, 53 mm. 20—21 mm. 99 Elgon. 



49, 49, 50 mm. 20 mm. 99 Eldoret. 



