AND DEVELOPMENT OF THE BIRD'S SKULL. 107 



In the adult of this species, the Carrion-Crow, the siphonium is enringed by the 

 lowest and largest of the seven hones that form the curious tympanic chain. Figures of 

 these have been given in my paper on the " Coracomorphse " in the ' Transactions ' of the 

 Zoological Society. 



The stapedial plate (st), turned a little forward for display, is continuous, as bone, 

 with the mediostapedial {mst), and then come the outspread leaflets of cartilage. The 

 " extrastapedial " (est) is sickle-shaped and broad-backed, its thick convex back being 

 strongly connected with the inner face of the membrani tympani (mty) ; and the fibres 

 of the perichondrial coat are interwoven with those of the drum-skin itself, and also meet, 

 from without, those of the tendon of the " tensor tympani " muscle (stm). 



The tongue-shaped rudiment of the suprastapedial (sst) lies in the base of a two- 

 winged membrane, the fibrous supplement of this part. 



The cartilaginous strap running downwards from the extrastapedial to the entering 

 carotid (ic) is the infrastapedial (ist) and stylo-hyal (sth) in one band. The fore end of 

 the mandible (mk, d) shows that, as in the Fish, the mandibular rods do not meet to 

 form a " mentum " in these prognathous types ; they keep distinct, and each receives 

 its own dentary. 



The form and disposition of these parts in the adult are shown in fig. 9. They are 

 those of the Daw ( Corvus monedula) ; the references are the same as in fig. 8. 



In the Crows of the southern world there are many important differences of structure 

 from what is seen in the northern species : notably, the condition of the stylo-hyal is 

 instructive. In the Piping Crow ( Gymnorhina tibiceri) the general structure corresponds 

 very exactly with that of Corvus ; but the stylo-hyal (figs. 10 & 11, sth) ends below in a 

 cheese-knife-shaped plate, which lies upon the outer edge of the basitemporal, and is 

 well ossified. Slender as in the mediostapedial shaft (mst), it is pneumatic and com- 

 municates with the tympanic cavity by both proximal and distal passages. 



Being desirous that this, together with the paper on the Fowl's Skull, should enable 

 the student to form an accurate conception of the skull of the Carinate Bird, as 

 distinguished not only from that of other classes, but also from that of the " Ratitse," or 

 Struthious order, I now proceed to show some of the most important modifications of the 

 ornithic face. Happily for me, I have at hand a strong and sharply expressed outline of 

 this subject ; and now it will be easy to make a more extended study and comparison of the 

 facial morphology of the higher birds (see Huxley's " Classification of Birds," Proc. Zool. 

 Soc. 1867, pp. 415-472). 



My former papers illustrate the " Dromseognathous " face as seen in the raft-breasted 

 Ostrich (Huxley, op. cit. p. 425) and the keel-breasted Tinamou (Phil. Trans. 1866, plates 

 ix.-xv. pp. 113-183) ; the " Schizognathous " face (Huxley, op. cit. p. 426), as seen in the 

 Common Powl (Phil. Trans. 1869, plates lxxxi.-lxxxvii. pp. 755-837) ; and the " JEgi- 

 thognathse " have been illustrated in the Zoological Transactions for 1875 *. 



I return now to the Sparrow-faced birds, " JEgithognathse " (see Huxley, op. cit. p. 450) . 



description, as that made the Bird differ from the Crocodile in the disposition of the pneumatic duct. It does differ, 

 as I have shown above. 



* See Part I., in vol. ix., plates 54^62. Part II. will soon appear. 

 SECOND SERIES. — ZOOLOGY, VOL. I. Q 



