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



D. Third postoral arch. 



Length and tenuity of hasal piece and upper and lower pieces of the cornua (thyro- 

 hyals, or 1st cerato- and epibranchials). 



E. Large size, but great simplicity, of nasal turbinal folds. 

 E. Cowrie-shaped tympanic cavity. 



Concluding Remarks. 



The " Celeomorph.Ee " of Huxley form a most natural and well-defined group — a group 

 equal, zoologically, to the Pigeons or the Parrots. Evidently this differentiation has 

 taken place through the gradual extinction, during long secular periods, of conjugational 

 types more generalized than those now extant. I am not without evidence as to the 

 truth of this view ; but it must be discussed elsewhere ; yet proofs will be given in proper 

 time and place. 



Those who are familiar with the Lacertian type of skull will agree with me as to the 

 propriety of such a morphological term for the Woodpeckers and "Wrynecks as " Sau- 

 rognathse." It will exactly fill up the lacuna left by my friend in the masterly paper 

 already referred to. The view there expressed that these birds have a Passerine foun- 

 dation, but that they are somewhat abortively developed, arrested one way and wonder- 

 fully specialized in another, will be seen to be the exact truth of the matter. 



Corresponding with what I am showing in papers for the ' Zoological Transactions,' 

 with regard to the " iEgithognathse (Passerine," " Coracomorphse"), the most embry- 

 onic and least specialized "Woodpecker is a South- American form, namely Picumnus. 



"We have seen how numerous the bony centres are in this group ; and it is not easy to 

 account for this peculiarity. They are very numerous in all birds, but least so in the 

 Thrushes (" Turdidee ") ; whilst in the " CoracomorphEe " generally there is an average 

 development as to numbers. There is some reason for these differences ; but it is hidden 

 amongst the extinct forms, both warm- and cold-blooded. 



Teleologically, the " Picidse " cannot possibly benefit by the numerous small bones 

 that have a temporarily separate existence in their palate, many of these being mere grains, 

 and others most feeble splints. 



The general agreement of the palate of Picumnus with that of the last of the Ehyn- 

 chosaurian Lizards (namely Hatteria) is very suggestive. In the low South-American 

 Passerinee, the " Eormicariidse " and the " Cotingidse," the essentially Keptilian face 

 shows itself most clearly. , 



But that which characterizes the whole of the " Celeoniorphse " is the want of fusion 

 of the parts of the palate at the mid line. This is evidently an ancient reptilian 

 " atavism." This must be admitted in a metaphorical sense, if not in an actual : it is a 

 remarkable verisimilitude, if not a real historic truth. 



