4 MR. W. K. PARKER ON THE MORPHOLOGY OF 



On the Structure and Development of the Skull in Picus (Gecinus) yiridis. 



The extraordinary complexity of the palatine structures in the Green "Woodpecker can 

 only be understood by reference to the unfused elements in the fledgling (Plate I, fig. 2, 

 for the palate as a whole, and Plate I. figs. 3-8, and Plate II. figs. 5-7, showing details 

 and sections). In the palatal view of the young bird the nasal structures are purposely 

 left out for the better display of the facial bones — that part of the lateral ethmoid which 

 belongs to the 1st prseoral, the " os uncinatum," being coloured, as it is an essentially 

 upper palatine element. 



Beginning at the apical region of the trabecule, we see rudimentary basipterygoids 

 set on the side of the basifacial region, where it begins to form the rounded "rostrum" 

 (Plate I. fig. 2, b.pg). This parasphenoidal under-balk sharpens in front, and ends 

 behind the free fore edge of the mesoethmoid. The prsemaxillaries have together a high 

 triangular outline, and the outer bar (dentary portion) ends behind by lying for some dis- 

 tance on the dentary region of the maxillary ; so that whilst many birds are isomorphic 

 of the typical " Teleostei " in having an internally placed " os mystaceum," this bird 

 exposes as large a maxillary margin as the salmon. The palatine processes of the prse- 

 maxillaries equal the solid part in length, and in breadth they equal the outer or 

 dentary bar. Their position also is somewhat analogous ; for they pass on the inside of 

 the " prsepalatine," whereas in many Passerines they pass on the outside. This reversed 

 situation of processes is seen again in certain delicate Australian Passerines, namely 

 Aeanthorhynchus and JPtilotis. The nasal processes of the prsemaxillaries are broad, 

 flat, and fibrous, and they show a median suture late in life. The " os uncinatum " {p. u) 

 is part of the " ectoethmoid," and becomes as large as its distinct symmorph in those 

 Parrots which have an imperfect suborbital bar. 



The symmetrical " vomers " are not at first easy to find at this stage, being very 

 small ; but by removing the palatine they can be seen as small styles, attached to the tips 

 of the long mesopterygoid processes (Plate III. figs 5 & 6, v, m.pg). The symmetrical 

 " septo-maxillaries " (s.mx) are also to be found, by careful search, on the inside of the 

 palatine bars ; one was seen on the right, and two on the left side. The pterygoids (pg) 

 are of moderate length, and they have a long styloid " mesopterygoid process " (Plate III. 

 figs. 5 & 6, pg, m.pg) ; on their upper surface the pterygoids have a free spur, pointing in 

 the same direction as the mesopterygoid : this is very long in the old bird (Plate III. 

 fig. 1,pg); it is peculiar to the " Picidse." The " epipterygoid " hook is aborted; and 

 the mesopterygoid not being differentiated, there is then an evident arrest of metamor- 

 phosis in this proximal pier segment of the pterygopalatine arcade. The prsepalatine 

 bar is normally long and slender ; it is closely wedged in between the maxillary style 

 and the retral palatine process of the prsemaxillary. At the middle this narrow part 

 ceases ; the broad posterior half is gently sulcate along its middle ; and the inner portion 

 sends forward a styloid interpalatine spur (Plate I. fig. 2, pa, i.pa). The " interpalatine 

 edges" of the two bones are almost parallel from the spur to the end of the base. The 

 broad part begins to narrow at its outer edge midway ; and forming an obtuse angle there, 

 the transpalatine is aborted. The upper edges meet at the mid line ; and thus the nasal 



