190 Ma. W. J. F. WILLIAMSON ON 



plumage ( i.e., witli the abdomen fully chestnut ) are onl}' foiiiid in 

 Japan and the islinds of the China seas. In the two specimens I have 

 obtained, one ( an apparently' fi^'Hy adult male, from Sriracha, South- 

 eastern Siam) has rufous onlj' on the vent and under tail-coverts, 

 while in tlie other (a younger male, from Bangkok), the vent, under 

 tail-coverts and under wing-coverts and axillaries are bright chestnut, 

 and traces of that colour extend np the abdomen. Gates further 

 states that the cause of this variation ia not known, but may be 

 attributed either to climatic reasons or to the interbreeding of this and 

 the next species, Petrophila ci/nnus. 



Habits, (if. Tliis is a cold weather visitor to Siam, from Japan 

 and Northern China. It is fond of perching on the roofs of houses and 

 on posts in gardens, and 1 have seen a Blue Roek-Tiirush, either of this 

 or the next species, on the rocks near the sea at Koh Lak, in Peninsular 

 Siam. The bird is usually found solitary, and not only do its liabits make 

 it easj' to observe, but mj' experience is that it has little fear of man, 



Distrihution. Recorded from Northern, Central, Soul hern-eastern 

 and Peninsular Siam. Judging by the number of specimens obtained 

 in the several divisions of the country, as noted in the Papers quoted 

 in the synonymy, it appears to be commonest in South-eastern Siam, 

 and to be rather rare elsewhere. Tliis is certainly the case in Bangkok, 

 where I have only obtained this bird once, in Januarj'. 



-U {693}. Petrophila cyanus (Linn.). Tfie Western Blue 

 Bock-Thrush. 



Mont i cola c II an m, G\'\i[e\\%io\\\e, .] own. N. S H. Siam I, p. 170; id, 

 1916, p. 47. 



Bescriptiun. Length about 211 mm. ( 9.5 in. ). In both sexes 

 the colouration ia very similar to that of P. solitaria, described above, 

 but without any trace of chestnut or rufous on the under parts. 



Hahits, cC'c. Precisely similar to those of the preceding species, 

 than which, however, it is much commoner, though not by any means 

 plentiful. I have obtained altogether five specimens iiere, during the 

 months of January and Februarj', and one at the beginning of Ajiril, 

 besides a few more in other parts of the country', from October to 

 February. 



Distrihution. Recorded, up to the present, only from Northern, 



JOnUN. NAT. MIST. SOC. .SIA.M. 



