144 ZOOLOGY 



d. Tubercles on segments xxviii-xxxi ; ill- 

 smelling ; purple-banded ... A. fcetida 



c-2. Tubercles on segments, xxxi and xxxiii . A. cattyosa 



c'3. Tubercles on segments xxvii, yxviii ; 



color reddish brown .... A. tumida 



c 4 . Tubercles on segments xxiv-xxx ; about 



100 segments ..... A. parva 



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



c 6 . Tubercles on segments xxix-xxxi (occa- 

 sionally xxix, xxx); number of seg- 

 ments, 150 . . . . . . A. rosea 



bz. Prostomium completely divides buccal lobe 

 [genus Lumbricus]. 



Ci. Tubercles on segments xxviii-xxxi ; red- 

 brown or purple ; about 120 segments . L. mbellus 



c 2 . Tubercles on segments xxxiii-xxxvi ; 



number of segments, 180 L. herculeus 



KEY TO THE PRINCIPAL FAMILIES OF AQUATIC OLIGOCH^STA 



i. Dorsal blood-vessels visible only in the anterior 



part of the body ; farther back, as intestinal 



sinus, disappearing underneath the intestinal 



glands . . . '.""'. Enchytrceidas 



a*. Dorsal blood-vessels running on top of food canal 



and visible throughout its entire length. 

 61. In each segment, except the first, contractile 



lateral blood-vessels Lumbriculidas 



b. 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 . . . . Tubiflcidce 



(Ex. Tubifex) 



c 2 . Dorsal and ventral vessels united in each 



segment by a lateral vessel . . . Naidw 



(Exs. Nais, Dero) 



