1899.] ON THE CRANIAL OSTEOLOGY OE THE TARROTS. 9 



During my various changes of venue I accumulated a rich 

 material of Enteropneusta, au account of which I shall shortly 

 publish in Part III. of my Zoological Results which are being 

 issued by the Cambridge University Press. 



Lastly, it was my happiness to discover a new type of Peripatus 

 in New Britain which differs from the South African, Australasian, 

 and Neotropical subgenera in the same respects — anatomy and 

 development — in which they differ from one another. It con- 

 stitutes thei-efore a fourth subgenus, which I have called Paraperi- 

 patus. With regard to Peripatus, the next point of interest centres 

 upon the new species — P. thoUoni, which has recently been described 

 by Mons. E. L. Bouvier from the Gaboon district (West Africa). 



2. On Characteristic Points in the Cranial Osteology of the 

 Parrots. By D'Arcy W. Thompson, C.B., F.Z.S. 



[Received November 16, 1898.] 



To discover anatomical characters such as might yield or help to 

 yield a natural classification of the Parrots has been the desire of 

 many oi'nithologists, but the search has availed little. Garrod's 

 abundant work has told us many facts in regard to the presence 

 or absence of an ambiens, of an oil-gland, of one carotid or two, 

 and other varying characters in a multitude of species ; but when 

 we come to put these data together the result is unsatisfactory, 

 and one is left with the impression that the several series of facts 

 are incoordinate and cannot be linked together in a single system . 

 When we find, for instance, that the collation of these facts places 

 in a single group Am, Psitfacus, PceocepJiahis, and Nestor, and in 

 another Stringops, Melopsittacus, and Agapomis, one is tempted 

 to think that the only thing proved is that the data are invalid or 

 antagonistic — in other words, that the several structures had really 

 followed diverse or parallel or convergent lines of modification 

 and evolution. While such internal structures seem to me to lead 

 to confusion by indiscriminate variability, the characters of the 

 skeleton are generally deemed too monotonously alike to present 

 features of significance. Even in Stringops, the osteological peculi- 

 arities of which are greater than those of any other form (except 

 perhaps Nestor), they are yet not conspicuous enough to have pre- 

 vented certain recent writers from remarking that the divergence 

 of Stringops from the other Parrots is not so great as it had been 

 supposed to be. 



There is indeed in most parts of the skeleton a very great 

 uniformity throughout the order, but in certain parts, for instance 

 the orbital ring (where the differences are well known, though ioi- 

 perfectly investigated) \ the hyoid bone (as Dr. St. G. Mivart has 



''■ Cf. Em. Blanchard, " Caracteres osteol. chez les Ois. de la faniille des 

 Psittacides," C. E. xliii. pp. 1097-1100 (1S5«), xliv. pp. 518-521 (1857) ; C. L. 

 Bonaparte, ibid. xliv. pp. 531-539 (1857). 



