144 ZOOLOGY 



ci. Tubercles on segments xxviii-xxxi ; ill- 

 smelling ; purple-banded ... A. fcetida 



Co. Tubercles on segments, xxxi and xxxiii . A. caliyosa 



r 3 . Tubercles 011 segments xxvii, xxviii ; 



color reddish brown .... A. tumid a 



r 4 . Tubercles on segments xxiv-xxx ; about 



100 segments ..... A. parva 



05. Tubercles on segments xxviii-xxx . A. subrubicunda 



c$. Tubercles on segments xxix-xxxi (occa- 

 sionally xxix, xxx); number of seg- 

 ments, 150 A. rose a 



6 2 - Prostomium completely divides buccal lobe 

 [genus Lumbricus] . 



Ci. Tubercles on segments xxviii-xxxi ; red- 

 brown or purple ; about 120 segments. L. ntbellus 



Co. Tubercles on segments xxxiii-xxxvi ; 



number of segments, 180 L. hercnleus 



KEY TO THE PRINCIPAL FAMILIES OF AQUATIC OLIGOCH^ETA 



a\. Dorsal blood-vessels visible only in the anterior 

 part of the body ; farther back, as intestinal 

 sinus, disappearing underneath the intestinal 



glands EnchytneMas 



rto. Dorsal blood-vessels running on top of food canal 



and visible throughout its entire length. 

 &i. In each segment, except the first, contractile 



lateral blood-vessels Lumbriculidas 



bo. Lateral vessels contractile only in anterior 



segments. 



Ci. Dorsal and ventral vessels united in each 

 segment, except in the first 5, by 2 

 lateral vessels Tubificidce 



(Ex. Tubifex) 



Co. Dorsal and ventral vessels united in each 



segment by a lateral vessel . . . Naidce 



(Exs. Nais, Dero) 



