540 Mr. R. Shelford on some 



more rounded tlian was the case in Stage 1. The foot is 

 very slightly flattened laterally ; the two-jointed hallux is 

 now completely turned backward, as in the adult ; the third 

 digit is the longest. Dorsally the digits and '^tarsns " are 

 covered with one row of rectangular scutes, ventrally with 

 granular scales, smallest on the sole and on the somewhat 

 swollen " heel " (junction of tibia and tarso-metatarsus). 



Dimensioyis. — Total length 157; upper mandible (to nostril) 

 14 ; lower mandible (to gape) 23 ; neck 44 ; antebrachium 

 16; manus 14; tibia 21 ; tarso-metatarsus 16; 3rd digit 7*5. 



Rhytidoceros undulatus. — A slightly older embryo than 

 that just described, but the differences between the two 

 are very slight. The position of the embryo in the egg is 

 shown in the figure ; each manus is bent at right angles to 

 the cubitus and lies under the throat, their tips almost 

 touching ; the right foot lies with the plantar surface upper- 

 most, the left with that surface outermost. 



The rectrices and remiges have just protruded, while 

 papillae marking the future major coverts are plainly to be 

 seen on the cubitus and manus ; no other papilhe, however, 

 can be distinguished. The beak is shorter than in the 

 corresponding stage of B. rhinoceros and rather deeper. A 

 small deposition of calcareous salts at the extreme tip of tlie 

 upper mandible is noteworthy ; I have not noticed it in 

 B. 7'hinoceros either at this or the subsequent stage. The 

 lower mandible bears the minute papillse on its anterior 

 edge already alluded to. The opening of the oil-gland, with 

 a surrounding ring of feather-papillee, is apparent. The foot 

 is as already described. 



Dimensions. — Total length 159 ; upper mandible 12; lower 

 mandible 21; antebrachium 20; tibia 19; tarsus 16; 

 hallux 7 ; 3rd digit 6-5. 



Stage 3. — Newly-hatched nestlings of Buceros rhinoceros and 

 Rhytidoceros undulatus. (PI. VIII. figs. 4 & 5.) 



Buceros rhinoceros. — The conical shape of the head, the 

 entire absence of feathers, and the loose and closely-wrinkled 

 skin are the most noteworthy features at this stage. The 



