100 
Ganl. Bull. Singapore 70 (Suppl. 1) 2018 
Fig. 19. Distribution and abundance of order Arhynchobdellida in the Nee Soon drainage. Solid 
circles indicate sites where representatives were collected and circle sizes are proportionate to 
abundance/numbers of individuals captured as reflected in the accompanying legend. 
Class CLITELLATA 
The class Clitellata are annelids which possess a “glandular girdle”, also known as 
the clitellum, giving them their name. This organ produces a substance which forms 
a cocoon in which the juvenile worms develop (Ruppert & Barnes, 1994). They are 
found in the terrestrial, freshwater and in marine ecosystems. Among the more familiar 
members of this class are the earthworms and leeches. 
Order Arhynchobdellida 
The leeches found in this order do not possess a proboscis. Some members have jaws, 
while others are jawless. They also possess multiple feeding methods, with some 
