86 KIX(;H()RX <^ CAVJ.EV, Stonu Petrels. [\^,toT 



was collected by Mr. Baxter, appears slightly heavier thrcmgh- 

 out, though it is of the same length as the bills of our other 

 si)ecimens before us, and also in IMathews' two nominal species, 

 F. royoniis and F. iiuio}iu}iatus: in his F. iiisularis and F. alisteri. 

 it measures 13 mm.^^ 



Middle toe and eluu\ — In (jur Hrskine X'alley specimen (A) 

 the measurement is 20.5 mm. ; in that C(jllected by Mr. liaxter 



(B) it is 21 mm., while in the "H. L. White Collection" specimen 



(C) it is 20 mm. It will be noted that the spirit specimen (B) 

 has a longer toe than either of the others ; variation which seems 

 to be due to shrinkage in the joints of the dried skins. 



Torsus. — The measurement of the tarsus varies slightly. In 

 the Erskine Valley specimen (A) it is 36 mm. long; in Baxter's 

 specimen (B) it is 35 mm., and in the "H. L. White Collection" 

 specimen (C) it is 37 mm. ; in F. royaiius it is said to be 35 mm., 

 F. iiisularis 38 mm., F. alisteri 36 mm., and /•". iniioniinafus 37 

 mm. It will be noticed that these measurements o\erlap, the 

 smallest being 35 mm., and the largest 38 mm. ; but the dilYer- 

 ence of 3 mm. is not a serious item even in such a small bird, 

 as the points from which the measurements ai^e made vary 

 slightl}- through shrinkage. This statement is borne out by an 

 examination of the tarsi of other species, and also by reference 

 to tabulations of characters given by Dr. Sharpe and other 

 authorities. 



Tail. — The tail of the Erskine \'alley specimen (A) measures 

 83 mm., Baxter's si)ecimen (B) about 76 mm., and the "H. L. 

 White Collection" specimen (Cj 79 mm.; that of F. royamis is 

 said to be 79 mm. long, F. iusitlaris 80 mm., F. alisteri 75 mm., 

 and F. innomiuatus 80 mm. The difference between that of F. 

 alisteri (75 mm.) and the Erskine X'allc}- specimen (83 mm. ) 

 being ecpial to only a third of an inch, we consider it a matter of 

 little importance. 



IJ'iiu/. — That of the Er.skinc \ alley specimen { A i is 15" mm. 

 long, lUixter's example (B) 153 mm., and the "11. L. White 

 Collection" specimen 160 mm.; in F. royaiius it is 1()0 mm., F. 

 iiisularis 168 mm., F. alisteri 165 mm., and F. iiiiioiniiiatus 160 

 mm. Again it will be seen that the measurements are variable, 

 and are in no way comparative to any (nher measurements. 



Total length. — It is difficult to determine what "total length" 

 means in the various works referred to. Sonic writers have 

 measured from the forehead to the tij) oi the tail ; others seem 

 to have measured from the forehead to the tip of the folded 

 wings, which stretch beyond the tail ; again, measurements have 

 been taken from the base of the culmcn to either of the other 

 ]K)ints mentioned. Some authors measure from the tii> of the 

 bill to the tip of the tail. These measurements depend on the 

 ]>osition of the head, and whether the bill is in line with the 

 body or pointing uj^wards when the bird is on its back; further- 

 more, the neck, or in fact the whole skin, may be either stretched 



