44 DESCRIPTIONS OF PREPARATIONS. 



Nouv. Arch, du Museum, 1867, p. 114. The name ' Prensiculantia ' or 'Pfotler' 

 was suggested by Illiger, Prodromus, p. 81, i8n s after Buttmann, as a substitute 

 for that of Glires upon the following grounds : ' Nota : nomen hujus ordinis a 

 celeb. Buttmann excogitatum est ut maniculorum instar manuum usus his Mam- 

 malibus familiaris indicetur, aliis e motus instrument desumtis notis toti ordini 

 communibus simulque characteristicis, deficientibus.' 



The differences between the Glires duplicidentati, s. Lagomorphi, represented 

 by the Rabbits, the ordinary Hares, and the Tailless Hares, and all the other living 

 Rodents, are so great, and those which separate the three other subdivisions of the 

 order, the Myomorphi, represented by the Mice, the Sciuromorphi, represented by 

 the Squirrels, and the Hystricomorphi, represented by the Porcupines and Cavies, 

 are so much smaller as to make it convenient to divide the order into two main 

 divisions or Suborders : viz. the Simplicidentati, comprehending the three sections 

 just mentioned, and the Duplicidentati, comprehending the Hares and Rabbits. 

 Of these last the following propositions may be made in contradistinction to the 

 Simplicidentati. 



They have, as adults, two small incisors placed behind the two large ones in 

 the upper jaw, these two pairs of teeth representing the anterior and the posterior 

 of the three pairs of early life. They have a larger number of teeth, in the 

 molar series, than any other Rodents. The incisors are surrounded by a perfect 

 zone, if not of enamel in the adult, at least of enamel membrane in the developing 

 tooth. The enamel of the incisors is not divisible into two layers. The incisive 

 and the optic foramina are, severally, confluent, and the bony palate greatly 

 reduced. The glenoid fossa and the articular condyle of the lower jaw are less 

 specialized to antero-posterior movement than is the case in other Rodents. The 

 coronoid process and the sockets for the incisors in the same bone are also less 

 specialized. Ossification is less perfect, as for example in the facial part of the 

 maxillary and in the basicranial bones. They have a canalis caroticus in the 

 tympanic, but no true alisphenoid canal. The fibula is anchylosed to the tibia, 

 but articulates with the os calcis. The placenta is not disc-shaped, but consists of 

 two or more lobes sessile on the chorion and clamped together by a saddle-shaped 

 decidua serotina. These differences appear to place the Lagomorphi at a much 

 greater distance from the group made up of the Hystricomorphi, the Myomorphi, 

 and the Sciuromorphi, than any one of those sections is from any other. Of them 

 the Hystricomorphi, especially as represented by the Cavies, come nearest to the 

 Lagomorphi; the Myomorphi should be placed centrally, and the Sciuromorphi 

 highest in position. 



Mr. E. R. Alston, P. Z. S. Jan. 1876, pp. 73, 74, has proposed the establish- 

 ment of a third Suborder, that of Glires hebetidentati, for the reception of the genus 

 Mesotherium found in South American Pliocene deposits, and represented by an 

 animal a little larger than the Capybara. This animal had the same number of 

 incisor teeth placed in the same way, viz. two above and four below, as the Hyrax ; 

 they were surrounded, not merely faced, with enamel, and were not brought to a 

 sharp cutting edge by wear, but came to present a transversely hollow blunt surface, 

 whence the name hebetidentati. The mandibular condyle and the glenoid fossa 

 were not specialized to perform the antero-posterior movements so characteristic of 

 the Simplicidentati, and the three anterior and upper molar teeth were convex out- 



