ON THE CLASSIFICATION OF THE ROTIFERA. 



27 



(b) The second form is a simple segment of a circle, placed on the ventral side 



above the mouth, fig. 2'2. 



(2) The BdelloicUc wreath is also of two forms : 



(c) The first, like the Rhizotic wreath [a), is a double wreath surrounding the body 



twice, and inclosing the mouth ; but, unlike the Bhizotic, it has two gaps 

 instead of one, viz. a dorsal gap between the points of flexure, and a ven- 

 tral gap in the upper wreath opposite to the mouth. 

 {d) The second form of Bdelloidic wreath is a mere furring of the corona on 

 its ventral surface, as shown in fig. 25. 



(3) The Plo'imlc wreath is very various in shape, but is never BJiizotic, while it is 

 Bdelloidic only in one genus.' 



Fig. 23.— Bdelloidic wreath (c), 

 from above. 

 {Rotifer cUHmis) 



Fig. 24. — Bdelloiilic wreath (c), 

 side view. 

 {Roli/er cUrinus) 



Fig. 25.— Bdelloidic wreath (d). 

 {Adineta vaga') 



(4) The Scirtopodic wreath is of Bdelloidic type. 



III. In the form of the trophi. 



If we disregard two genera ' of the Flo'ima (not one-fifteenth of the whole number 

 of Ploimic genera), we can then say that the first three orders differ also in the forms 

 of their trophi. For — 



(1) The Bhizotic trophi are either mallco-ramate,^ fig. 2G, or uncinate,^ fig. 27. 



(2) The Bdelloidic trophi are always ramate,^ fig. 28. 



(3) The Ploimic trophi are of various forms ; but are never Bdelloidic, and are 

 Rhizotic only in two genera.^ 



(4) The Scirtopodic trophi are of a Rhizotic type, being malleo-ramate, fig. 26. 



Fig. 26. — Malleo-ramate. 

 {Melicerta nnijciis) 



Fig. 27. — Uncinate. 

 {SteptuLiioceros Eichhornii ) 



Fig. 28.— Hamate. 

 {Rotifer cittinus) 



Now, in reviewing the points of agreement and of difference m the four orders, we 

 may at once set aside the fourth order, the Scirtopoda, as unmistakably separated from 

 the others. 



This order contains but one family, which has only one genus, and that genus 

 itself consists of only one species.^ In fact, it has been formed to contain that 

 remarkable creature Pedalion viirum, which I discovered at Clifton in 1871. This 



' rterodina. - Triarthra and Pterodina. 



' For the explanations of these technical terms, see p. 29. 



' I pass over for the present Dr. Schmarda's llcxarlhra polypicra, and will discuss it under the 

 Fedalionida:. 



