1887.] 



ANATOMY OF HYDROMYS. 



61 



lobes, the supernumerary pair being placed behind and below the 

 others. 



Alimentary Canal and Appendages. 

 Teeth. — The dentition is as described by Owen^ I. \, M. 



2 

 2 ' 



the 



total number thus being smaller than that of any other Rodent. 

 The incisors closely resemble those of the Common Rat. 



The upper incisors are stouter and shorter than the lower ; they 

 are set closely together, their edges meeting at their inner angles, so as 



Fio;. 4. 



/^ 



Fig. 3. Left hand of Hi/dronujs chrysogaster. (Natural size.) 

 Fig. 4. Left foot of Hydromijs chrysogaster. (Natural size.) 

 Fig. 5. Upper and lower incisors oi Hydromys chrysogaster: a, inter- 

 mandibular muscle ; h, tongue. 



to enclose a wide angle (vide fig. 5). The portion projecting beyond 

 the alveolus is 1'05 cm. in length. The first upper molar is a 

 large tooth, consisting of two segments of nearly equal size and a third 

 of lesser magnitude {vide fig. 6, b and c). It possesses three large 

 fangs, one at either extremity and the third at the middle and on the 

 lingual edge. At the opposite side of the tooth to this last are tliree 



' Odoutograph}-,' vol. i. p. 410, and Comp. Auat. of Yert. vol. iii. p. 300. 



