230 ON THALASSIDROMA NEREIS. 



Amongst the Petrels mentioned at various times by the late Prof. 

 Garrod as having been examined by him, a species several times occurs 

 which is doubtfully named " Procellaria (or Thalassidroma) fregata ? " * 

 The specimens dissected by him are now before me, and have been 

 identified by Mr. Salvin as being really referable to the Procellaria nereis 

 of Gould, an example of which, from the Falkland Islands, is now in the 

 museum of Messrs. Salvin and Godman. A careful examination of the 

 three spirit-specimens of this bird, as well as of the skin mentioned, 

 has convinced me that this species is not referable to the true genus 

 Procellaria as represented by Procellaria pelagica, and is in fact in no 

 way related to that group of Petrels, but has its nearest allies in the flat- 

 clawed genera Oceanites, Fregetta, and Pelagodroma. 



In his paper on the muscles of the thigh in Birds t the late Prof. 

 Garrod divided the Nasutae, or Petrels, into two groups, the " Storm- 

 Petrels " and the Eulmaridae, the former group differing from the latter 

 in that they possess the accessory semitendinosus muscle (T), but lack 

 intestinal caeca. In the Fulmaridae, on the other hand, the accessory 

 semitendinosus muscle is absent, but caeca are present. The species of 

 Storm-Petrels on which this generalization was based are called, with 

 doubt J, "Procellaria pelagica and P. fregata" the latter being the 

 P. Z. S. 1881, species now identified by Mr. Salvin as P. nereis. As regards the first- 

 p. 736. named species, there can be little or no doubt that the bird really dissected 

 by Prof. Garrod, and called by him " 'Procellaria pelagica" was Wilson's 

 Petrel (Oceanites oceanicus), as in this bird there are no caeca , at the 

 same time that the accessory semitendinosus muscle is present. The 

 true Procellaria pelagica (of which I have lately dissected two perfectly 

 fresh examples) agrees with the Fulmaridse, as defined by Prof. Garrod, 

 in having cseca ||, but no accessory head to the semitendinosus ; and 

 Cymochorea leucorrlioa agrees in both these points with Procellaria 

 pelagica. 



The so-called " Procellaria nereis " of Gould is therefore obviously not 

 a true Procellaria at all ; and this view is confirmed by other characters, 

 such as the shape of its nostrils, the elongated tarsi, which are much 

 longer than the mid toe U" and covered anteriorly with transversely 



* Cf. P. Z. S. 1873, pp. 470 and 641. 



t P. Z. S. 1874, p. 122. J P. Z. S. 1873, p. 641. 



Cf. also Macgillivray, in Audubon's ' Ornithological Biography/ v. p. 646. 



|| Cf. Macgillivray, I.e. p. 313 ; also Wagner in Naumann's ' Vogel Deutschlands,' 

 x. p. 556. 



^[ In Procellaria pelagica and Cymochorea leucorrlioa the tarso-metatarse is not 

 longer, and may be shorter, than the 3rd toe. As against 21 '5 and 21 '5, and 23 and 26 

 millitn. in the two first-mentioned genera, in the so-called Procellaria nereis the lengths 

 of the two are respectively 34 and 26 millims. 



