1847.| BOWERBANK ON THE PTERODACTYLUS GIGANTEUS. 9 
liar modifications of the bone-cells which characterize fishes, and is 
represented by fig. 7. Pl. I. This modification of the bone-cells is 
perhaps the nearest form among fishes to those of the reptilia. The 
normal form in fishes is an angular or nearly square cell, with large 
canals radiating from it in various directions. From these there is a 
transition of form until they assume the appearance represented by 
fig. 7, and in some cases the large canals radiating from this form of 
cell unite, and the whole then forms a plexus of canals of nearly equal 
diameter. 
I cannot conclude this paper without expressing my thanks to my 
friend Mr. John Quekett for the very liberal manner in which he 
communicated to me the results of his own laborious and valuable 
researches on the structure of bone, which were subsequently com- 
municated to the Microscopical Society in a paper read the 18th of 
March 1846, and which will, I feel convinced, prove a most valuable 
means of deciding disputed relations of obscure and difficult tribes of 
recent animals, as well as of pointing out at once to us the true rela- 
tion of such geological remains of the animal kingdom as it might 
be otherwise exceedingly difficult, or perhaps impossible, from their 
dilapidated condition, to refer to their true position among animals. 
Average length and greatest diameter of five Bone-cells, from each 
of the specimens treated of in the above Paper. 
Name of Animal. Length. | Diameter. |Proportion. 
inch. inch. 
Pi SRE Ask ATURE SOT Oe OM. 1-805 | 1-3261 |1 to 4 
Mebimae Cl 1, fir D)ossewsais oe aspires cate ° 1-688 | 1-4274 |l to 6% 
Bterodactyle Jaw (Pl.D:fig. P)y asic cece ne ai 1-552 | 1-6024 | 1 to 11 
Lord Enniskillen’s specimen (Pl. I. fig. 2)....| 1-515 | 1-6173 | 1 to 12 
tebe SMEs (El Diets cece ce esse ce es 1-519 | 1-5882 |1 to 115 
Mersey Smith’s:(PR AL fied). ie. oe as 1-493 | 1-5814 | 1 to 11 
CPIMIGr Pro esis 0s tkiels ols « Vo. otek. 1-392 | 1-4629 | 1 to 113 
SRM OMGLTICON + Spice) biayois xed egdne ead ore ois s ove 1-561 | 1-6097 |1 to 11 
Thylacotherium Prevostii (Pl. I. fig. 6) ...... 1-980 | 1-4032 |1 to 4% 
Vertebra from Stonesfield (Pl. I. fig. 4) ...... 1-1087 | 1-4500 |1l to 44 
Bone from Wealden, No. 453 B. M. (PI.I. fig. 8)} 1-787 | 1-7812 |1 to 10 
Do. Do. No. 2353 B.M. (PII. fig.9)} 1-855 | 1-4505 {1 to 52 
DESCRIPTION OF PLATE I. 
Fig. 1. A group of bone-cells from the jaw of Pterodactylus giganteus. 
2. Bone-cells from the specimen represented by fig. 1. Pl. 39. vol. vi. 2nd 
Series Trans. Geol. Soc., in the possession of the Earl of Enniskillen. 
3. Bone-cells from a femur of recent Albatros. 
4. Bone-cells of vertebra from Stonesfield slate. 
5. Bone-cells of jaw of Thylacotherium Prevostii, fig. 1. Pl. 5. vol. vi. Trans. 
Geol. Soc. 2nd Series. 
6. Bone-cells from Thylacotherium Prevostii, fig. 3. Pl. 5. vol. vi. Trans. 
Geol. Soc. 2nd Series. 
7. Bone-cells from Mr. Toulmin Smith’s fossil fish from the Chalk, figured in 
the London Geological Journal, vol. i. page 22. 
