1 88 AQUATIC MICROSCOPY FOR BEGINNERS. 



these appendages bearing few small conical thorns or 

 none. The body-margins are fringed 

 by short spines. The central space 

 on the ventral aspect between the 

 two longitudinal, lateral bands of cilia, 

 is beset with short, fine, recurved 

 prickles, and five or more long bristles 

 project from the same surface beyond 

 I 8 — chffiWnotus ^^^ border of the posterior bifurca- 

 acanth6des tJQn, while on each side of the body 

 near the posterior extremity there are two large re- 

 curved spines. The animal is usually found among 

 Sphagnum. 



5. Ch«t6notus spfNiFER (Fig. 139). 



Among Riccia and Lemna in shallow ponds this 

 well-armored form is not rare. Tne upper surface is 

 covered by rounded imbricated scales, the free margins 

 directed forward. From each scale arises a stout, 

 recurved, unequally and minutely furcate spine, whose 

 base is enlarged and thickened. These spines do not . 

 commonly originate from the center of the scales, but 

 near the posterior part, and between the margins of 

 those- laterally contiguous. The spines are largest 

 and stoutest on the back proper, decreasing gradually 

 over the neck and head, and rapidly over the posterior 

 parts, while across the dorsal surface immediately in 

 front of the caudal bifurcation extends a supple- 

 mentary series of four thorns, longer and stouter than 

 those on any other part of the body. The posterior 

 region of the space between the longitudinal ventral 

 bands of cilia bears five bristles, arranged to form a 

 long triangle, the apex pointing forward. 



