1887.] 



ANATOMY OF HVDROMYS. 



63 



dwelt upon. The lower first molars consist of two nearly similar 

 segments placed one in front of the other ; and the second are much 

 the same in appearance but smaller (vide fi";. 6, a). 



Tongue. — 4'6 cm. in length ; it has an average breadth of TO cm. 

 It possesses a single large cireumvallate papilla, situated at the centre 

 near the posterior part. There is a small group of folia on either 

 side in front of the anterior pillar of the palate. 



Intestinal Canal. — The stomach is simple in structure, and the chief 

 points to be remarked upon are the increase in size of the pyloric 

 portion and the decrease in length of the part corresponding to that 

 named in the human subject the lesser curvature (^vide fig. 7). The 

 small intestines measure 2 m. 89"5 cm. ; the large 27"8 cm. ; and the 

 caecum about 7*0 cm. This latter portion is quite simple and onlv 

 slightly curved upon itself (vide fig. 8). 



Eig. 8. 



Caecum of Hydroinys chrysogaster. (Natural size.) 

 Co. Colon ; II. Eeum ; Coc. Cseenro. 



Liver. — This organ possesses six lobes. The right lateral is short 

 and permits the caudate, w'hich is comparatively long, to be seen 

 upon the upper surface. It appears between the right central and 

 lateral lobes. There is no gall-bladder (vide figs. 9 and 10). 



Genitalia. — The vesicidae seminales are very long and narrow, 

 extending a considerable distance above the bladder. Their length 

 is 5'6 cm., average breadth about TO cm. The testes are large and 

 were, when the animal was examined first, placed in the scrotum. 

 The length of each is 4*2 om., circumference 6'2. In life these 

 measurements would probably be larger, as they were made after the 

 animal had been in spirit and water for a day or two. The globus 

 major and minor are very distinct and united by a single tube which 

 is perfectly straight. The length of major is 4-8 cm., minor 2*1. 

 There is a small os penis (I'l cm. in length), consisting of a some- 

 what square-shaped base with a tapering anterior portion. From 

 each side of the base a small process descends, each of which lies on 



