Hood — On the Rotifer a of the County Mayo. 677 



Floesoma hnticulare — continued. 



inaccurate ; the dorsal view given by Wierzejski and Zacharias 

 (I.e., pi. xiii., fig. 7) is perhaps the best that has appeared. In 

 both this last and in Levander's figure the median vertical 

 grooves are represented as entirely separate from one another, 

 the point of view not showing their posterior apical junction. 



The most striking point in regard to the relation of this species 

 to Ehrenberg's E. lynceus is the complete omission from Ehren- 

 berg's description of any allusion to the two conspicuous transverse 

 median furrows ; this omission seems of itself conclusive proof that 

 the species are not the same. Whether Ehrenberg's species be, on 

 the other hand, identical with one of the other closely allied species 

 now known to us, for instance the very distinct G. truncata, 

 Levander (of which Mr. Eousselet has kindly sent us American 

 specimens collected by Mr. Jennings) is another question which 

 may, in the meantime, be left open for discussion. 



The systematic position of the Eotif er is not yet settled, and in- 

 volves many difficulties, which difficulties are indeed only increased 

 when we take into account such undoubtedly allied species as 

 P. i^Gastroschiza) flexilis^ Jagerskiold = Bipalpus vesiculosus, "Wierz. 

 .and Zach. It is plain, that these species are not closely allied to 

 Euchlanis, and it is likewise plain, both that they fall into none 

 of the received families of the Loricata, and that it would not be 

 easy to form for their reception any single new family whose 

 definition should conform with the definition of the families at 

 present accepted. Levander, it is true, groups these allied species 

 under the new family Grastroschizidse, but does not essay a 

 definition of the family thus constituted. Mr. Jennings cuts the 

 knot of the difficulty by placing Ploesoma in the family Hyda- 

 tinidae, on the ground of its obvious general and anatomical 

 resemblance with the typical species of ISTotops. Professor D' Arcy 

 Thompson entirely agrees with this view, and it is accordingly 

 here accepted. It involves the dispensing altogether, in this case, 

 with lorical characters ; and if characters drawn from the lorica 

 be found valueless in this instance as a guiding principle in 

 classification, it is more than possible that in many other cases 

 also they are in reality fallacious. In short, though this is not 

 the proper place to suggest a new classification of rotifers, we 

 may simply say that it seems likely that ere long a new classifica- 

 tion of the Ploima will be required, in which the characters of 

 the lorica will take a very subordinate position. 



