Bibliographical Notice. 3 1 7 



BIBLIOGRAPHICAL NOTICE. 



Zoological liesults based on, Material from New Britain, New Guinea^ 

 Loyalty Islands, and elsewhere, collected daring the Tears 1895, 

 1896, and 1897, by Arthur Willey, D.Sc. Land., Hon. M.A. 

 Cantab., late Balfour Student of the University of Cambridge. 

 Bart III. Cambridge, 1899. 



The third part of Dr. Willey's 'Zoological Results' contains only 

 three articles, but each of these is in its own way a valuable contri- 

 bution to zoological literature. 



The iirst paper is by Dr. Hans Gadow and is entitled " Ortho- 

 genetic Variation in the Shells of Cheloiiia." Dr. Gadow bases his 

 remarks on an examination of the shells of 20 newly-hatched 

 specimens of the Loggerhead (Thalassochelys caretta), collected by 

 Dr. Willey from one nest in New Britain, and of numerous 

 individuals of various ages in different museums. Altogether his 

 material comprised 76 specimens. The arrangement of the epi- 

 dermal scutes in these specimens showed considerable variation, 

 especially in the yonnger individuals, and Dr. Gadow, looking upon 

 these variations as atavistic, draws from them important conclusions 

 as to the evolution of the carapace in the Chelonia. The gist of 

 these conclusions is contained in the following extract : — ■ 



" At an early ancestral stage, not necessarily that of the pri- 

 mordial Chelonian, the plates and scutes of the back were arranged 

 as follows : — All the metameres carried originally a series of 

 transversely arranged dermal plates and scutes, which in the region 

 of the trunk, according to the greater bulk of the body, increased 

 in size, converging towards the root of the neck and upon the tail. 

 About 14 metameres were distinguished by the greater size of the 

 dermal plates, each transverse series consisting of a median or 

 neural and three pairs of lateral elements, in all eight. The 

 median pair fused into an unpaired neural. The next lateral pair 

 became the costal, the outermost or most lateral the marginal set. 

 The intermediate row between these two still survives in some 

 recent genera as the so-called supramarginals ; it became gradually 

 suppressed owing to the increasing size of the costals. 



"The last costals, say those of the loth to 20th metameres, became 

 likewise suppressed in conformity with the shaping of the trunk ; 

 the three last neurals were turned into pygals and the last pair of 

 marginals closed round the posterior end .... A similar reduction 

 seems to have taken place at the root of the neck .... 



" A later phylogenetic sLage would be characterised by the 

 suppression of the supramarginals, and by the reduction from 

 eight to seven to six and ultimately to even less transverse series 

 of exiidermal scutes, while the constituting elements of the dermal 

 armour after having been welded into the formation of the carapace 

 remain comparatively constant."' 



A remarkable feature of this process of reduction of the epidermal 

 scutes is that it takes place (in the life-history of the Loggerhead) 

 not by loss of scutes at either end, but by the elimination of eiCi r^nts 



