PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
191 
would subject the serpent to considerable inconvenience. 
When a fang is lost, however, another is almost ready to 
take its place on the opposite side of the same jaw; and 
there may be no less than five pairs in different stages of 
development to replace those that are lost. In the lizards 
the teeth are confined to the jaws and palate. In the 
crocodile they are found on the jaws only, implanted in 
sockets, and are formidable on account of their size and 
sharpness. 
Birds .—No recent bird has teeth. In the merganser the 
jaws are serrated, and serve the purpose of teeth in pre¬ 
venting the escape of slippery prey. The discoveries of 
Professors Marsh and Owen, however, have shown that 
some extinct birds were well supplied with teeth. 
The paper was illustrated by diagrams, preparations, 
and models. 
January 8th, 1885. 
F. Buchanan White, M.D., F.L.S., President, 
in the Chair. 
NEW MEMBERS. 
The following were elected :—Major Dudgeon, Depute- 
Governor, General Prison, and Mr Wm. Anderson, Bal- 
housie School. 
The following were nominated for election at next 
meeting :—Miss Wippell, City and County Infirmary ; 
Mr Wm. Roy, West Cultmalundie ; Dr P. M'lver 
Campbell, Perth District Asylum, Murthly ; Mr James 
Dewar; J. Grahame, Esq., Sheriff-Substitute; and Mr 
John MTntosh. 
donations. 
I. Index Collection. —Branch with cones of Cedar of 
Lebanon, grown at Airleywight—from Messrs Dickson & 
Turnbull; mineralogical specimens from Mr Galloway, 
Perth. 
II. Perthshire Collection. —Three moles, three shrews, 
one water shrew, one long-tailed field mouse, six red 
field voles — from Mr D. Dewar, Remony, Kenmore ; 
six long-tailed field mice, thrw squirrels, two stoats— 
from Mr W. Laidlaw, Castle Menzies ; one jackdaw— 
from Mr W. Duncan, Almondbank; one hanging wasp’s 
nest—from Mr C. Gibson, Pitlochry; one common hare 
(curious pale variety)—from Mr John Hood, Drummond 
Castle; one otter—from Lord Stormont, Scone Palace; 
one common rat and four rick mice—from W. Herd, 
Scoonieburn; pure white variety of common rat—from 
Lord Stormont; great black-backed gull—from Mr J. 
Forbes, Kilgraston; a large number of labels for the birds 
—from Colonel Drummond Hay; stoat and greater black- 
backed gull—from Mr Irvine, Dupplin; variously-coloured 
pearls from the pearl-mussel (Unio margaritifer) of the 
Tay—from Dr Buchanan White. (Note. —Specimens of 
white pearls are much desired to complete the series.) 
Black variety of common rabbit—from Mr P. D. Mallocb, 
Perth; white variety of common sparrow—from Mr Black, 
Strathview. 
III. Library. —“A List of Diurnal Birds of Prey,” by 
J. H. Gurney—from the author. 
The following papers were read : — 
1. “ Comparative Anatomy of the Teeth. II. Mam¬ 
malia." By Mr James Stewart, L.D.S. 
In the mammalia the teeth are fewer in number than in 
fish or reptiles. They are always confined to the jaws, and 
there are never more than two sets. The perpetual replace¬ 
ment so common in fish and reptiles finds no parallel 
amongst the mammals. When only one set is present, 
the teeth, with few exceptions, very closely resemble each 
other; but when there are two sets they differ from each 
other in form and size. We are thus enabled to give the 
latter special names, as follows :—1. Incisors, the teeth 
implanted in the intermaxillary bone, and the correspond¬ 
ing teeth of the lower jaw. 2. Canine, the first tooth 
behind the intermaxillary suture, provided it is not far 
behind it (the under-canine closes in front of the upper). 
3. Molars, those at the back of the mouth, which come 
up behind the first or deciduous teeth (these are 
generally broad and strong, and used for grinding 
the food). 4. Premolars, those in front of the molars, 
which have displaced deciduous teeth. 
In past ages, the teeth of mammals were much simpler in 
form, and more closely resembled each other, and it was only 
by progressive modification and suppression that the denti¬ 
tions have attained their present complexity. In a certain 
extinct animal, the Bomolodontotherium, the incisors, 
canines, &e,, pass by insensible gradations into each other, 
the adjacent teeth differing but little from each other. In 
