MACKIE — ON FOSSIL BIRDS. 



23 



Dennis thinks there can be no doubt ; and he therefore proceeds to 

 attempt to discover what kind of bird it might have been. " We have 

 no reason," he says, " to suppose it belongs to the Raptores, for it 

 does not exhibit their peculiarities of structure, the Haversian tubes 

 being peculiarly large in the diurnal birds of prey. Neither did it 

 with much probability belong to the Corvidse, for in them they are 

 finer and more reticulate ; still, neither did it belong to the Colum- 

 bidse or the gallinaceous family." All the goose, duck, and gull tribes, 

 with the divers, perhaps mergansers or cormorants, may also be ex- 

 cluded, for they are reported, as far as Mr. Dennis has examined 

 them, to have marked distinctions. By this process of separation, Mr. 

 Dennis narrows the field of research, and " leaves us with the cranes, 

 herons, egrets, and bitterns, and birds of that description," to dis- 

 cover a living representative of this ancient bird. He then attempts 

 to show that " our common heron exhibits a very marked agreement in 

 many particulars." "The bones of the heron, like those of other 

 animals, exhibit a varied adaptation of their Haversian tubes, and 

 certainly do not compare with the fossil in some of them, — as the 

 tibia, for instance ; but in the humerus there is a very great similarity, 

 more so than in the ulna or radius. The Haversian tubes in the 

 humerus appear to be constructed on the very same plan, so that a 

 description of the one would be a counterpart of the other, only they 

 appear rather larger in the heron. The lacunse have also the same 

 shapes, with nearly the same admixture of round ones, the heron 

 appearing to have a greater number. The canaliculi also per- 

 fectly agree. Supposing the fossil bone to have been a humerus, 

 its correspondence with the humerus of the heron would indicate 

 that its wing was similar in shape, and its mode of flight correspond- 

 ing." " Should further investigations," Mr. Dennis concludes, " sub- 

 stantiate this surmise, it will be another triumph of the microscope 

 in the field of science." To these remarks Mr. Dennis adds 

 " Addenda," which contain excellent remarks for obtaining exam- 

 ples of, and preparing bone-structure for microscopic examination, 

 that may be read with much benefit by students and others interested 

 in this subject. 



Mr. Dennis's paper is accompanied by a plate (Micr. Journ. vol. 

 v. pi. vi.), in which the following figures of microscopical sections 

 are given: — 1. Pteropus ; humerus. 2. Bat; phalanx. 3. Flying 

 Pbalanger ; tibia. 4. Draco volans ; ulna. 5. Red-throated Diver; 

 tibia. 6. Swift; furcula. 7. Mr. Catt's fossil (Pterodactyls). 8. 

 Pelican ; bill. 9. Stonesfield fossil, vertical section. 10. Ditto, 

 transverse section. 12. Heron; humerus. 13 a. Heron; humerus. 

 b. Stonesfield fossil ; lacunse, 14. Mr. Catt's fossil (Pterodactyle) ; 

 lacunse. 16. Heron ; lacunse. 17. Gannet ; humerus. 18. Ditto ; 

 coracoid. 19. Ditto ; furcula. 20. Ditto ; femur, vertical section. 

 21. Ditto ; femur, transverse section. 22. Ditto ; tibia. 23. Ditto ; 

 tarsus. 24. Ditto ; rib. 



Of these, we have reproduced in our Plate V., as essential to the 

 understanding of Mr. Dennis's arguments, fig. 9 to 16, namely the 



