74 TUCKERMAN. [Vol. VII. 



the organ, and is continued on to the under surface for a short 

 distance. Fungiform papillae are sparingly scattered over the 

 dorsum. The raised posterior division of the tongue, more con- 

 vex than the anterior, is 12 mm. in length and 8 mm. in breadth. 

 The general character of the surface agrees with that of the 

 anterior division. There is a single circumvallate papilla situ- 

 ated in the median line, 5 mm. from the base of the organ. As 

 in Fiber zibethicus and Hesperomys leucop?is, the trench is anteri- 

 orly incomplete. The lateral organs are but faintly visible, and 

 lie anterior to the circumvallate papilla. 



GUSTATORY STRUCTURES. 



The Circumvallate Papilla. — The papilla measures 0.36 mm. 

 in diameter and 0.50 mm. in height. The immediate area 

 around it is unpapillate. The summit is flattened or slightly 

 rounded, and overtops somewhat the adjacent lingual surface. 

 The walls are perpendicular or nearly so, and the trench narrow 

 and deep. Serous glands are plentiful, and their ducts open 

 into the trench at its deeper part. Mucous glands are also 

 abundant in this region ; and their ducts, which exceed in 

 diameter those of the serous type, traverse the mucous mem- 

 brane, and open obliquely on the free surface. 



The taste-bulbs are present on the lateral area of the papilla 

 and in the epithelium of the outer wall of the trench. They fill 

 the sides of the papilla to within a short distance of the top, and 

 they reach the same level on the outer wall. The number of 

 tiers in each region appears to be ten. The average number of 

 bulbs in a tier of the papilla is thirty, the average number in a 

 tier of the outer wall being about forty. Owing to the trench 

 being incomplete the number of bulbs is relatively decreased. 

 They are fairly uniform in size and shape, and measure 0.060 

 mm. in length and 0.032 mm. in breadth. Occasionally, isolated 

 bulbs occur on the upper surface of the circumvallate papilla in 

 Mtis decumantis. 



The Lateral Gustatory Organs. — The organs are 1.15 mm. in 

 length and 0.40 mm. in breadth. Each consists of three or 

 four folds, all of which bear bulbs on their lateral area. The 

 folds are separated by narrow furrows, slightly dilated at their 

 base, and having an average depth of 0.20 mm. The mucosa com- 



