SOME SCOTTISH ROTIFERS 163 



P. aculeata, Ehr. Extremely variable. The spines are typically 

 twelve in number, arranged in pairs on the back, the pair most 

 laterally placed pointing forward. The spines may be reduced 

 to mere tubercles, and they may be less than twelve in number. 

 The texture of the skin also varies greatly. It is sometimes 

 smooth, sometimes papillose, and rarely beautifully and regularly 

 rugose. Frequent, Mallaig, Lochinver, Fort Augustus. 



P. roseola, Ehr. In my experience this typical species of the genus 

 is rare. Blantyre Moor, Fort Augustus. 



P. citrina, Ehr. Not common, Blantyre Moor, Inverness-shire. 



P. erythrophthalma, Ehr. Mr. Bryce identifies as this species a 

 lanky active animal frequent in the sediment of bog pools. It 

 is a most voracious feeder, and will swallow diatoms so large 

 that one wonders how they get through the gullet. When 

 feeding it is restless, bending from side to side. It often 

 swims. Blantyre Moor. 



P. obesa, Murray. Distinguished by its stout form, dental formula 

 3-3, and tubercle between the spurs. Rare only one 

 example yet seen, Blantyre Moor. 



P. brevipes, Murray. This is distinguished from the other large 

 species of the genus by its short foot, which has only three 

 joints. It is like P. erythrophthalma in its restless habits when 

 feeding. The dental formula consists typically of two large 

 teeth on each ramus, with a thinner one bounding the groove 

 which receives the opposite tooth. This is a common formula 

 in Bdelloids, the thinner tooth being anterior on the one ramus 

 and posterior on the other. In this species the third tooth is 

 frequently enlarged so that there seems to be three equal teeth 

 on each ramus. The animal appears to be liable to attack by 

 various parasites. The commonest consist of large round 

 nucleated cells, of what nature has not been ascertained, which 

 float in the body fluid. In one district all the specimens had 

 a coating of hair-like fibres on the oral segments. 



P. nemoralis, Bryce. Frequent, Loudoun Hill, Fort Augustus. 



P. acuticornis, Murray. Both the spurs and corona show a consider- 

 able amount of variation. The spurs are usually small, 

 straight, divergent, and acute, but they are sometimes very 

 slender, almost setiferous. The skin is usually very minutely 

 stippled, rarely even papillose. The sulcus of the corona 

 varies in width. The folds of skin continuing the collar 

 terminated in rounded expansions a little way below the summit 

 of the upper lip. In creeping, it is seen to be a heavy 

 bodied animal with very slender foot. Common, Blantyre 

 Moor, Fort Augustus. 



