STRUCTURE OF FOSSIL BONE. 75 



thickness ; reticulate, but without any precise form or size in 

 the loops, but rather a marked irregularity is shown, some 

 appearing square, others triangular, others oval, in fact of 

 all shapes and sizes; sometimes they somewhat interlace; 

 they do not entirely maintain a uniform diameter, the reti- 

 culations are inclined to form combinations, which produces 

 a variety in their appearance, sometimes two or three of 

 a similar shape and size uniting. The lacunae are numerous, 

 small ovals, and round, but more pointed ones than round. 

 The canaliculi are fine, much branched, and very numerous. 

 That this is the bone of a bird, fi'om the evidence I have 

 adduced, there can be no doubt. My object is rather now 

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

 We have no reason 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 Corvida, for in them they are finer and more reticulate ; 

 still, neither did it belong to the Cohmibidce or the gallina- 

 ceous family. All the goose, duck, and gull tribes, with the 

 divers, perhaps mergansers, cormorants, &c., may also be 

 excluded, for they have, as far as I have examined them, 

 marked distinctions. By this process of separation we have 

 narrowed the field of our research, which leaves us with the 

 cranes, herons, egrets, and bitterns, and birds of that 

 description, to discover a living representative of this ancient 

 bird. But for the present, I shall only attempt to show that 

 our common heron exhibits a very marked agreement in 

 many particulars. 



The bones of the heron, like those of other animals, exhi- 

 bit a varied adaptation of the Haversian tubes, and certainly 

 do not at all 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 Haver- 

 sian tubes in the humerus appear to be constructed on the 

 very same plan, so that a description of the one would be 

 only the 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 

 perfectly 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 corresponding. Should further investigations 

 substantiate this surmise, it will be another triumph of the 

 microscope in the field of science. 



VOL. V. H 



