94 The Molluscan Family Planorhidae 



Remarks. Australorhis is so peculiar in certain of its anatomical char- 

 acteristics as to puzzle the systematist regarding its proper position in the 

 classification of the family Planorbiclae. In its narrow penial complex with- 

 out penial gland it is related to Tropicorbis. The prostate, however, is very 

 different from any member of the Planorbinae and superficially resembles 

 some of the Helisomatinae in the presence of multiform diverticula. The 

 ovotestis is also of a multiform nature. The prostate diverticula are also 

 attached directly to the sperm duct instead of to a separate prostate duct 

 as is the case in Tropicorbis. In this respect, the prostate of Australorbis 

 resembles that of the genus Drepanotrema, the few diverticula in this 

 group being attached directly to the sperm duct. The kidney is of the 

 Helisoma type, with a distinct ridge. 



In spite of the multiple nature of the diverticula of the prostate and 

 ovotestis, the group appears to be related to Tropicorbis and to be correctly 

 placed in the subfamily Planorbinae. The absence of a penial gland re- 

 moves it from Helisomatinae and Planorbulinae and the absence of a 

 flagellum, and also the form of the shell (with overlapping whorls), ex- 

 cludes it from the subfamily Segmentininae. When the characteristics of the 

 prostate are closely examined it is seen to be uniserial in form in spite 

 of the branched nature of the diverticula. Each diverticulum arises from 

 the sperm duct as a single tube, the branching taking place after the 

 diverticula are above the sperm duct. So also in the ovotestis, each divertic- 

 ulum arises from the ovisperm duct as a single tube, the branching being 

 on one side only. 



In the Helisomatinae, both the prostate and the ovotestis have the 

 diverticula radiating from the ducts like the spokes of a wheel, in fan- 

 formation. The ridged kidney is an exception in the Planorbinae. This 

 characteristic, as well as the apparent multiple appearance of the prostate 

 and ovotestis, may show ancient affinities with the Helisomatinae. Austra- 

 lorbis is apparently an aberrent genus of the family. 



Pilsbry has suggested (1934, p. 56) that it might be considered a sub- 

 genus of Tropicorbis but this procedure would appear untenable because 

 of the peculiar prostate and ovotestis as well as the ridge on the kidney. 

 Pilsbry did not examine the ovotestis or the kidney. 



The name Planorbina Haldeman was used for this group by Dall in 

 1905, the Brazilian species Planorbis olivaceus Spix and Wagner being 

 designated as the type. Germain, in 1921, selected Planorbis guadaloupensis 

 Sowb., as type of Planorbina. But as Pilsbry states in his description of 

 Australorbis, neither olivaceus nor guadaloupensis answer to Haldeman's 

 description 'whorls numerous, nearly equal,' the whorls in these species 

 increasing in diameter to such an extent that the last whorl is notably 

 wider than the preceding whorl. Haldeman's Planorbina is now considered 

 a synonym of Anisus. Pilsbry 's discussion of the reasons for rejecting the 

 types proposed for Planorbina, for which no type was designated by 

 Haldeman, by Dall or Germain are well stated and do not need to be 

 repeated here. 



Genus ANISOPSIS Sandberger. 1875 



Type herein nominated Planorbis calculus Sandberger 



1875. Anisop.sis Sandberger, Land imd Slissw. Conch, der Vorwelt, p. 958. No type 

 cited 



1905. Anisopsis Dall, Alaska Moll., p. 81. Plaiwrbis loryi Coq., and Planorbis cal- 

 culus Sandb. cited as examples 



