154 LEECHES 



2. Eyes, 5 pairs forming lateral crescents as in Fig. 1 ; 

 5 annuli per segment in the mid body region ; pharynx 

 short, less than quarter-length of body ; mouth armed 

 with toothed jaws; testes in large sacs arranged 

 segmentally in pairs. 



Suborder Gnathobdellae 4 



— Eyes, 3 or 4 pairs arranged in two transverse rows as in 

 Fig. 2; 5 annuli per segment or number increased by 

 sub-division of annuli; pharynx long, about one- 

 third length of body ; mouth with muscular ridges but 

 no jaws; testes in small, numerous bunched sacs. 



Suborder Pharyngobdellae 



Family Erpobdellidae 53 



3. Body at rest depressed, not divided into distinct 

 anterior and posterior regions; head usually much 

 narrower than the body with anterior sucker not, or 

 only slightly distinct from the body; usually 3 annuli 

 per segment in the mid body region; eyes confined to 

 the head except in Placohdella hollensis. 



Family Glossiphoniidae 5 



— Body at rest cylindrical and (especially when con- 

 tracted) usually divided at segment XIII into distinct 

 anterior and posterior regions; head sucker usually 

 distinctly marked off from the body; usually more 

 than 3 annuli per segment ; simple eyes may be present 

 on head, neck and posterior sucker. 



Family FiscicoLiDAE ( = Ichthyobdellidae) .. 31 



4. Eyes, 5 pairs, the third and fourth separated by 



1 annulus (Fig. 1). 



Family Hirudidae . . 40 



— Eyes, 4 pairs, the third and fourth separated by 



2 annuli (Fig. 3). 



Family Haemadipsidae 52 



Section 2. Key to the Family Glossiphoniidae 

 5. Mouth within the anterior sucker cavity, on segments 



