44 ART. 4. — I. IKEDA : 



basal border. The wall of this shield is unusually thick aud 

 hard on account of the deposition of a calcareous substance. Its 

 surface is sculptured into numerous longitudinal ridges and 

 grooves that converge towards the rounded apex. When examined 

 under a certain magnification, the ridges are seen to be covered 

 with small chitinous bodies of a deep brown color (Fig. 73), and 

 at the hindmost end of each ridge there is situated a large 

 papilla consisting likewise of chitinous l)odies similar to those of 

 the remaining part of the ridge. The center of this papilla 

 shows a circular space formed of small and light-colored plates 

 and surrounded by 2-3 rings of very dark-colored plates. The 

 apical parts of the shield are stripped of the ej)idermis, thus 

 exposing the underlying wdiite calcareous layer. The skin-surface 

 adjacent to the shield is closely beset with papillae which 

 appear as deep brown spots. These latter are structurally the 

 same as those of the papilhe lying at the l:)asal border of the 

 anal shield, though they are somewhat smaller. In the middle 

 and posterior regions of the body, the papilke are quite flat, and 

 are formed of many polygonal chitinous plates separated from 

 one another by narrow grooves (Fig. 74). These plates are smaller 

 towards the center of the papilla, where the pore of the subdermal 

 gland is situated. The caudal shield is not definitely marked 

 off, but is simply indicated by a darker brown color. The aperture 

 of the introvert lies just below the ventral border of the anal 

 shield, so that the introvert as a whole stands out nearly at 

 right angle from the body proper. The introvert is about as 

 long as the body ])rope]', and is of a light yellowish bi'own color. 

 The anterior portion carries numerous complete ring-rows of 

 hooks which are 0.04 vim. long and of a reddish yellow color 

 (Fig. 75). Between these rows are scattered tubular papilkie 



