APPENDIX A 155 



II-IV; body only moderately flattened; salivary glands 

 diffuse ; no oesophageal pouches 6 



— Mouth on anterior rim of sucker (Fig. 4) body often 

 excessively flattened ; salivary glands usually compact; 

 oesophageal pouches often present 20 



6. Eyes, 4 pairs arranged as in Fig. 5 ; body (except when 

 distended with eggs) soft and translucent; small, 

 hungry leeches strap shaped with dilated head, but 

 mature recently fed leeches almost globular. 



Theromyzon Philippi 1884 7 



— Eyes fewer than 4 pairs; body usually opaque and firm 10 



7. Gonopores separated by 2 annuli 8 



— Gonopores separated by more than 2 annuli . . . . 9 



8. From Central Europe. 



Theromyzon maculosum (Rathke 1862). 



— From North America. 



Theromyzon m^jym (Livanow 1902). 



9. Gonopores separated by 3 annuli. 



Theromyzon rude (Baird 1863). 



— Gonopores separated by 4 annuli. 



Theromyzon tessulatum (O. F. Miiller 1774). 



10. Head and anterior sucker when at rest rather broader 

 than the body segments just behind them (Fig. 6); 

 eyes, 2 pairs on annuli 3-5 ; colour green or pale yellow 

 with 7 longitudinal rows of lemon yellow spots; size 

 at rest about 17 X 5 mm. 



Hemiclepsis marginata (O. F. Muller 1774) 



— Head and anterior sucker not wider than the body 

 segments just behind (Fig. 7); eyes not arranged as 



in Fig. 6 ^ 11 



11. Eyes, 1 pair, simple, well separated ; small leeches at rest 

 about 10 mm long. Helohdella E. Blanchard 12 



— Eyes more than 1 pair, or if 1 pair these are lobed 

 showing that they have been formed by the fusion of 

 several eyes (Fig. 8) 15 



