330 Royal Institution. 



section of the crown is bilobed. The teeth of the Glyptodon were 

 fluted by two analogous grooves on each si4e. The large molars of 

 the Capybara and Elephant have the crown cleft into a numerous 

 series of compressed transverse plates, cemented together side by side. 



The modifications of the crown of the molar teeth are those that 

 are most intimately related to the kind of food of the animal pos- 

 sessing them. Illustrations were given of the chief of these modi- 

 fications in the purely Carnivorous mammals, where the molars are 

 simple, trenchant, and play upon each other like scissor-blades : in 

 the mixed feeding species where the working surface of the molars is 

 flattened or tuberculated : in the insectivorous species where it is 

 bristled with sharp points : and in the purely herbivorous kinds, 

 where the broad grinding surfaces of the teeth are complicated by 

 folds and ridges of the enamel entering the substance of the tooth : 

 the most complex forms being presented by the Elephants. 



Teeth of each of the kinds above determined, and arbitrarily named 

 "incisors," "canines," "molars," have received other special names, 

 in regard to certain peculiarities of form or other property ; and the 

 ablest comparative anatomists have been led astray in determining 

 their homologies when they have suifered themselves to be guided 

 exclusively by morphological characters. The small anterior grind- 

 ing teeth in the human subject have been called " bicuspids." The 

 penultimate upper tooth and the last lower tooth in the Lion are 

 termed, from their peculiar form, "sectorials," or " carnassial teeth," 

 ** molaires carnassieres " of Cuvier. Teeth of an elongated conical 

 form, projecting considerably beyond the rest, and of uninterrupted 

 growth, are called "tusks;" such are the incisors of the Elephant 

 and Dugong, and the canines of the Boar and Walrus : the long and 

 large incisors of the Rodents have been termed, from the shape and 

 structure of their cutting edge, scalpriform or chisel-teeth, " denies 

 scalprarii.'* The inferior incisors of the flying Lemurs {Galeopithecus) 

 have the crown deeply notched like a comb, and are termed " denies 

 pectinatiJ'* The canines of the Baboons are deeply grooved in front, 

 like the poison-fangs, " denies cmialiculati,''^ of some serpents. The 

 compressed conical crowns of the molar teeth of the small clawed Seals, 

 Sienorhynchus, are divided either like a trident into three sharp points, 

 or like a saw, into four or five points ; the molars of the great extinct 

 Zeuglodon had a similar form ; such teeth have been called denies 

 serraii. But the philosophical course of the knowledge of nature 

 tends to explode needless terms of art, invented for imimportant 

 varieties, and to establish and fix the meaning of those words that 

 are the signs of determinate species of things. 



The Cuviers divided the molar series of teeth, according to their 

 form, into three kinds : " false molars," " carnassials," and " tu- 

 bercular molars ;" and, in giving the generic characters of Mam- 

 malia, based the dental formulae on this system : thus the genus 



2 2 



Felis is characterized as having " fausses molaires 2lIo» carnassieres 



j^, tuberculeuses r^ j = -v." 

 In a diagram of the leading modifications of Diphyodont dentition. 



