242 MR. J. W. GEEGOEY ON THE 



regards Adeonellopsis as based only on the possession of a peristomial pore he declines 



to accept it. 



Mr. Waters's conclusions [No. 6, p. 294, and No. lo, pp. 3, 32, 33] are very different; 

 he abandons Adeona as a synonym of Microporella, and speaks of the type species as 

 Microporella grisea, form Adeona ; in his last essay he accepts Adeonella for forms 

 without a trypa but with a peristomial pore, the latter a character of very doubtful 

 value. 



Mr. Macgillivray's conclusions [No. 2, pt. ix. p. 134] seem to me more, though not 

 entirely, satisfactory. He accepts Adeonella in much the same sense as Mr. Waters ; but 

 he fully grasps the significance of the absence of the trypa and removes the genus 

 to the MucronellinecB (or Smittidae). He agrees with Mr. Hincks and differs from 

 Mr. Waters in separating Adeona from Microforella owing to the absence of external 

 ooecia in the former ; finally, he founds the genus Adeonellopsis for forms resembling 

 Adeonella, but without a peristomial pore. 



Before proceeding to discuss these views 1 must again express my thanks to my 

 colleague Mr. Kirkpatrick for allowing me constant access to the recent species, and 

 especially to Busk's type specimens, and also for the opportunity of frequent discussion 

 of all the points involved. 



The first point to be decided is what are the true afiinities of Adeonella. The first 

 species described by Busk was A. polymorpha, and this he seems to have regarded as his 

 type ; Mr. Waters certainly includes it in the genus as restricted by him. Mr. Hincks 

 [No. 4, pt. xiii. pp. 294-296] has quoted Busk's remark [No. 8, p. 183] that " as 

 regards the general zooecial characters there is no difi^erence whatever between Adeona 

 and Adeonella" This remark seems to me quite inexplicable. Adeonella poly- 

 morpha has no trypa, which seems to be generally regarded as implying a difl'erence in 

 family. A. polymorpha is therefore not one of the Microporellidge at all, and cannot be 

 synonynous with Adeona, which has a trypa *. Macgillivray has clearly recognized 

 this, and has removed Adeonella to his Escharidse. But this seems to me to be going 

 rather too far ; in Adeonella polymoipha and all the species which seem to be con- 

 generic with it, the primary orifice is always schizostomatous, and therefore the 

 genus cannot enter the holostomatous group : its true affinities appear to me to belong 

 to the Schizothyriata allied to the Schizoporellidse ; the secondary orifice appears to 

 distinguish it from both the Schizoporellidse and the Microporellidse ; the presence of 

 goncecia instead of external ooecia still further separates it from the Schizoporellidse, 

 but allies it to its old associates of the Adeonince. Its true position therefore appears 

 to be as a distinct family intermediate between the Schizoporellidse and the Micro- 

 porellidsB, with one link attaching it to each. 



* Macgillivray's figures of Adeona {Dictyopora) cellulosa show an occasional absence of the trypa [Macgil- 

 livray, No. I, dec. V. pi. 47. fig. 1 a, 6]. A dissection of a specimen with the same feature shows that it is 

 duo simply to the trypa being overgrown and concealed by the avicularium. 



