$6 ELEMENTARY BIOLOGY. [CHAP. 



a. The prominent eyes with their eyelids. 



/3. The membrana tympani, a thin part of the in- 

 tegument stretched over a hard ring, on each 

 side, behind and somewhat below the eyes. 



y. The anterior nares ; two small apertures near 

 the middle line at the end of the snout. 



8. The mouth-opening; note its boundaries and 

 extent. 



e . The browspot ; lying in the mid dorsal integu- 

 ment of the head on a level with the front of the 

 eyes. Clearly visible under a hand lens. 



t Open the mouth widely; the fleshy tongue will 

 be seen, with its bifurcated free end turned 

 backwards ; teeth are present only in the upper 

 jaw and on the roof of the mouth. 



b. The trunk. 



Tapering towards the hinder end, and allowing 

 the hard parts of the skeleton to be felt beneath 

 the soft integument on the dorsal side, and in 

 the anterior half of the ventral aspect. Note the 

 cloacal aperture near the dorsal surface of its 

 posterior end. 



c. The limbs. 



a. The anterior pair; their three subdivisions, 

 brackium, antebrachium, and manus ; the four 

 digits. 



/?. The posterior pair; their length as compared 

 with that of the anterior ; their subdivision into 

 femur, crus, and pes: the five long digits; the 

 well-developed web; the horny prominence on 

 the inner side. 



