NO. 2164. REVISION OF ROTATORIAN GENERA— EARRING. 535 



L. hidentata Voronkov, L. horealis, new species, L. heterostyla (Mur- 

 ray), L. ehrenbergii (Perty), and L. pterygoida (Dunlop). To the 

 Metopidia-groiip must be referred: Lepadella imhricata Harring, L. 

 rhomhoides (Gosse), L. cristata (Rousselet), L. rhomboidula (Bryce), 

 L. triptera Ehrenberg. The lateral projections of L. ehrenbergii and 

 pterygoida are probably of specific value only, as may be inferred 

 from the variations of L. latusinus. In extreme cases this has 

 lateral spurs rivalling in size those of L. eJirenhergii, and yet furnishes 

 a complete series of forms limited at the other extreme by a variety 

 with a posterior emargination differing but little from that of L. 

 ovalis. The same is apparently true of the longitudinal ridges de- 

 veloped in a number of species, conspicuously so in L. quinquecostata 

 and pterygoida. If this peculiarity really possessed any generic or 

 subgoneric value, these two species would be expected to possess 

 other characteristics in common ; as a matter of fact they agree only 

 in the generic characters. 



KEY TO THE GENUS LEPADELLA. 



1. Dorsal plate convex, without prominent median ridge 2 



Dorsal plate with prominent median ridge, body triradiate in cross section . . .17. 



2. With distinct anterior dorsal sinus 3. 



Without distinct anterior dorsal sinus 13. 



3. Depth of anterior dorsal sinus less than 1/2 width 4. 



Depth of anterior dorsal sinus more than 1/2 width 9. 



4. Toes equal 5, 



Toes unequal 8. 



5. Toes fused at base 13. borealis, new species. 



Toes not fused at base 6. 



6. Lorica with two prominent dorsal ribs and two curved lateral projections. 



16. pterygoida (Dunlop). 

 Lorica without prominent dorsal ribs 7. 



7. Foot groove very wide 4. latusinus (Hilgendorf). 



Foot groove not very wide, a median ridge on dorsal and ventral plate. 



5. amphitropis, new species. 



8. Lorica rhomboid, edges upturned anteriorly 14. heterostyla (Murray). 



Lorica with two curved lateral projections, edges not upturned. 



15. ehrenbergii (Perty). 



9. Lorica rounded posteriorly 10. 



Lorica with a posterior point 12. 



10. Dorsal plate with longitudinal ridges 6. quinquecostata (Lucks). 



Dorsal plate without longitudinal ridges 12. 



11. Lorica strongly depressed 2. ovalis (Miiller). 



Lorica not strongly depressed 3. patella (Miiller). 



12. Posterior point ^vith basal inangulation 7. cryphaea, new species. 



Posterior point mthout basal inangulation 8. acuminata (Ehrenberg). 



13. Toes equal 14. 



Toes unequal 11. cyrtopus Harring. 



14. Posterior margin with a median lobe between two small spines. 



12. hidentata Voronkov. 

 Posterior margin rounded, without spines 15. 



15. Anterior dorsal margin slightly concave 10. benjamini, new species. 



Anterior dorsal margin slightly convex 16. 



