AND DEVELOPMENT OF THE BIRD'S SKULL. 105 



the Fowl, stands as the head of another group, the " Alectoromorphae ;" and this 

 represents also a broad and goodly family of forms. In another paper, " On the Classi- 

 fication and Distribution of the Alectoromorphse " (Proc. Zool. Soc. 1868, pp. 294-319), 

 our autbor has broken this fine family into fragments, separating (see pp. 302-304) 

 not only the Pigeons (" Peristeromorphse "), which are " Altrices " and have tender 

 young, but the Sand-Grouse also, as the " Pteroclomorphse," and the Hemipods as " Tur- 

 nicimorpha3." As they stand at present, no cutting and contriving will make the 

 lesser groups, such as the " Charadriomorphse," " Pteroclomorphae," and the like, 

 correspond to or in anywise be the equivalents of the great army comprised under the 

 Crow form. Much as I value my friend's paper, I do but consider it in the light of a 

 sign-post to guide others who are footing it on the same road, and not as a finished work 

 to rest in. 



In one of the most outlying of the Crow forms, the House-Martin (Chelidon urbica), 

 I have been able to demonstrate the second morphological stage of the second postoral 

 arch. I did not succeed in this point in the Fowl ; but now that it is done it will do 

 duty for the whole of the " Sauropsida." 



The metamorphosis of this, as of the other arches, has been fully worked out in the 

 " Ichthyopsida," in my researches on the skull of the Frog and the Salmon; but 

 neither of these throw any fight upon the long-stalked, trifoliate stapes of the Reptile 

 and the Bird. Professor Huxley, in his paper " On the Representatives of the Malleus 

 and Incus " (Proc. Zool. Soc. 1869, pp. 391-407), says (p. 398), " the suprastapedial 

 cartilage " [he is describing the parts in Sphenodon\ " turns out to be nothing more 

 than the proximal end of the hyoidean arch, while the stapes and its appendages are 

 exclusively related to this arch, and have nothing whatever to do with the mandibular 

 arch." 



True ! and yet he does not say how much of the stapes belongs to the auditory capsule. 

 In the Urodela the stapes is cut out of that capsule, like a bung, and in Batrachia the 

 head of the upper segment of the hyoid arch articulates with the auditory stapes, its 

 uppermost part being segmented off as a " pars orbicularis." In the Mammalia the 

 Batrachia are closely followed (Phil. Trans. 1874, plates xxvi.-xxxvii.). In my former 

 paper on the Fowl's head (plate lxxxi. figs. 5, 9, & 10, st) I showed, in the second stage, 

 a thick somewhat flattened club of cartilage, the knobbed end of which fitted into the 

 fenestra ovalis, whilst the other or distal incurved end was trifoliate, the upper process 

 being the " suprastapedial " rudiment, the lower the " infrastapedial," and the longer, 

 bowed leaf the " extrastapedial." 



In a young Eave-Swallow, at about the same period, the upper end was seen to be 

 continuous with the periotic capsule in front of its fusion with the exoccipital cartilage, 

 and above the outer end of the rudimentary cochlea. This stapedial bar (Plate XX. 

 fig. 7, wist) has the characteristic curve of the summit of the facial arches, and at this 

 stage has coalesced with the auditory capsule as is the wont of these bars (see the 

 quadrate in continuity with the periotic cartilage, as figured in Huxley's ' Elements,' 

 p. 138, -fig. 57, F 1 Qu). This is undoubtedly the second or coalescing stage of the 

 second postoral ; it has, however, only coalesced by the strong posterior head ; the 



