1908.] DR. KI^UD ANDERSEN ON BATS, 205 



Artibeus*. 272 of these specimens (218 skulls) form part of the 

 collections of the British Museum; the rest, 213 specimens 

 (143 skulls), were placed at my disposal, for inspection and 

 identification, by the Authorities of the United States National 

 Museum. 



The British Museum series is particularly rich in South and 

 Central American, the Washington series in Mexican and West 

 Indian specimens. Thus the two collections admirably supple- 

 ment each other. 



I wish to tender my grateful thanks to Mr. Oldfield Thomas 

 for the opportunities he has so kindly afforded me for continuing 

 my Chiropteran studies in the British Museum. To Dr. J. 

 Leisewitz, Munich, Dr. Marcus W. Lyon, Washington, and 

 Professor D. G. Elliot, Chicago, I am indebted for information on 

 typical specimens in the collections under their charge. 



The Dentition of Abtibeus plaxirostbis. 



The teeth of one species only, viz., Artibeus j^lanirostris (subsp. 

 fallax) are described in detail in this paper, the description of the 

 dentition in the other forms being, as a rule, confined to those 

 points in which it differs from this paradigma. 



On the denomination of the molar cusjis. — The molar cusps are 

 named in accordance with Herluf Winge's theory f. The three 

 cusps (labial in the upper, lingual in the lower jaw) forming the 

 tips of the W of a tjq^ical molar in insectivorous bats are termed, 

 in antero-posterior direction, respectively 1, 2, 3, cusp 2 being pro- 

 bably the oldest, homologous with the single cusp of a Eeptilian 

 tooth ; the two cvisps forming the bases of the W are named 4 

 and 5 ; the " heel " of the upper molars, when single, cusp 6, 

 when double, cusps 6 and 7. See text-figs. 40, 41, pp. 207, 208. 



i^ i- — c p' p^ m^ m^ m' 



looth jormida. 



lo ^ Pi Pi "^1 ^o ^3 



Remarks on the tooth formida. — Xo known bat has more than 

 two pairs of upper incisors. The generally accepted hypothesis 

 is that the permanently missing pair is i^ ; but, in my opinion, 

 the balance of evidence is decidedly in favour of the view that 

 i^ not i\ has been lost. The former hypothesis (i^ lost) is 

 generally supported by two arguments, viz., '• by the corre- 

 spondence of the two upper teeth with the two outer of the lower 

 jaw when the maximum set Ls present," and " even more strongly 

 by the general tendency thi'oughout the group [i. e.. the Chiro- 

 ptera] for the j)remaxillaiies to become reduced, particularly 

 along the inner edge " %. As to the former argument, it proves 



* Brief preliminary diagnoses of the genus EncJnsthenes and ten new foiins of 

 Artiheus and Vroderma were published in the Ann. & Mag. Nat. Hist, for December 

 1906 (pp. 419-423). 



t Herluf Wino 

 Former 



1 Ge 



