194i DENNIS, ON CETACEAN BONES. 
form separately bands or stripes parallel with the Haversian 
tubes_, or surrounding tliem_, as the section may happen to be 
made. Between these bands appear the other distinct and 
characteristic lacunae^ which for the sake of distinction I 
shall term free lacunae^ as the others^ for the same reason^ 
may be called Haversian lacunae. These distinctions are not 
any peculiarity in the bones of Pachyderms^ and are equally 
shown in those of Cetaceans. In an inquiry, then, of this 
sort, we have to consider, amidst a general resemblance, the 
nice and real points of difference. In the comparison of 
mammalian bone, the question is more one of degree than 
anything else ; Cetaceans present a coarser character of bone 
than Pachyderms. At an early period of my investigations 
I was somewhat misled by engravings of whalers bone, from 
which I thought that the canaliculi of its bone were nume- 
rous and fine ; actual observation teaches me that such is not 
the case. The canaliculi in all cetacean bone are, for mam- 
malian bone, coarse, and easily distinguishable from those of 
the elephant, &c. I have now examined both the Greenland 
whale, sperm whale, dugong, manatee, dolphin, porpoise, 
walrus, and seal, and find this cliar act eristic of all — the dolphin 
and seal approaching the nearest in respect of fineness to the 
elephant; for even the ivory-like rib-bone of the dugong 
exhibits canaliculi visibly coarse in comparison with those 
seen in Pachyderms. 
In cetacean bone, especially in the Greenland whale, sperm 
whale, and porpoise, as also in others in a less degree, the ' 
canaliculi of the free lacunse very often branch out in a long* 
and straggling manner, as shown at PL XIII, fig. 10; and this 
appears to be a distinctive characteristic of the whale's bone, and 
more so in the Greenland than the sperm whale ; it is also well 
seen in the porpoise, &c. The bones of both the elephant and 
whale which have been obtained from the Drift are generally 
very perfect as to their microscopical characters. In the fossil 
whale, the free lacunae having coarse, few, and straggling 
canaliculi, give a very clear and distinctive character to its 
bone, while the greater number and greater fineness of them 
in the elephant sufficiently distinguish the bone of that 
animal from the whale. The greater general regularity of 
the free lacunae in Pachyderms, both as regards form and 
direction, affords another test. The canaliculi of the Haver- 
sian lacunae of both the Greenland and sperm-whales often 
run into one another, or dilate in portions of their course, 
especially at the ends, which is a marked distinction from the 
fine and delicate characters of those of the elephant. The 
Haversian tubes, when they are better understood, will also 
