1881.] MR. W. A. FORBES ON THALASSIDROMA NEREIS. 735 



1, On the Petrel called Thalassidroma nereis by Gould, 

 and its Affinities. By W. A. Forbes, B.A., E.L.S.^ 

 F.Gr.S., Prosector to the Zoological Society. 



[Eeceived May 17, 1881.] 



In this Society's Proceedings for the year 1840, the late Mr. 

 Gould described a " beautiful fairy-like " new species of Stormy Petrel 

 from Bass's Straits, which he called Thalassidroma nereis (torn. cit. 

 p. 178), under which name it is figured in the last volume of the 

 'Birds of Austraha.' 



Dr. Elliott Coues, in his revision of the family Procellariidse', 

 treating of the species under the name Procellaria nereis, says : — "I 

 have had the {)leasure of examining Mr. Gould's types of this 

 species from Bass's Straits, Australia, now in the collection of the 

 Philadelphia Academy. It is a beautiful little species, quite unlike 

 any other known Stormy Petrel. In form it comes nearer to Pro- 

 cellaria jielagica than to any other species ; and it is probably 

 congeneric with it, though it differs somewhat" in the proportion of 

 the tarsus and toes, and very widely in its pattern of coloration.* * * 

 The proportions of the tibia and tarsus differ from those oi'pelagica in 

 the greater comparative length of the former." 



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 Thalassidrorda)fregataV'^ 

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

 identified by Mr. Salvia as being really referable to the Procellaria 

 nereis of Gould, an example of which, from the Falkland Islands, is 

 now in the muse\mi of Messrs. Salvia and Godman. A careful exami- 

 nation of the three spirit-specimens of this bird, as well as of the 

 skin mentioned, have 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 ^ the late 

 Prof. Garrod divided the Nasutse, or Petrels, into two groups, the 

 "Storm-Petrels" and the Fulmaridse, the former group differing 

 from the latter in that they possess the accessory semitendinosus 

 muscle (Y), but lack intestinal cfcca. In the Fulmaridpe, on the 

 other hand, the accessory semitendinosus muscle is absent, but caeca 

 are present. The species of Storm-Petrels on which this generali- 

 zation was based are called, with doubt^" Procellaria pelagica and 

 P.fregata," the latter being the species now identified by Mr. Salvin 



^ Proceedings of the Academy of Natural Sciences of Pliiladelphia, 1864, 

 p. 81. 



- The italics are mine. — -W. A. P. 



3 Cf. P. Z. S. 1873, pp. 470 and CA\. 



' P. Z. S. 1874, p. 1 21. 3 P, Z. S. 1873, p. 641. 



