MACKIE — ON FOSSIL BIEDS. 
28 
DenDis thinks there can be no doubt ; and lie 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 Eaptores, 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 Corvidae, for in them they are 
finer and more reticulate ; still, neither did it belong to the Colum- 
bidae 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 fur as Mr. Dennis has examined 
them, to have marked distinctions. By this process of separation. Mr. 
Dennis narrows the iield 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 lacunae have also the same 
shapes, with nearly the same admixture of round ones, the heron 
appearing to have a greater number. Tiie canaliculi also per- 
fectly agree. Supposing the fossil bone to have been a humerus, 
its correspondence witii the humerus of the heron would indicate 
that its wing was similar in shape, and its mode of flight correspond- 
ing." " Should furtiier investigations," Mr. Dennis concludes, " sub- 
stantiate this surmise, it will be another triumpli 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 
Phalanger ; tibia. 4. Draco volans ; ulna. 5. Ked-throated Diver; 
tibia. tJ. Swift; furcula. 7. Mr. Catt's fossil (Pterodactyls). 8. 
Pelican ; bill. 9. Stonesfield fossil, vertical section. . 10. Ditto, 
transverse section. 12. Heron; humerus. 13 Heron; humerus. 
h. Stonesfield fossil ; lacunae. 14. Mr. Catt's fossil (Pterodactyle) ; 
lacunae. 16. Heron; lacunae. 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. 21. 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 
