196 PUPELLIDAE AJSTD RELATED GROUPS. 



(Miill.) is reproduced (pi. 29, fig. 1), and by Watson (1920). 

 Neither describes the internal structure of its penis, but its 

 appendix (ap') appears shorter than in StroMlops (less so in 

 Watson's fig.) and one branch of its penial retractor (re) 

 inserts on the epiphallus (ep). Its radular central is little 

 over half as wide as its 1st lateral. 



Anatomical notes on Spelaeodiscus triarius (Rossm.) are 

 given by Hesse (191-5) and by Soos (1917). If I interpret 

 the latter 's figures correctly, its oviduct, spermatheca, vagina, 

 prostate, apical caecum of the epiphallar penial arm and 

 penial appendix must be extremely like those of Strohilops; 

 about the only salient differences appear to be the much larger 

 appendicular arm of its penis, the insertion of one branch of 

 its penial retractor below the middle of this appendicular 

 arm, and its radular central, which is about % as wide as the 

 1st lateral and appears to have vestigial ectoeones. The two 

 genera are also similar in shell form and texture. 



On the basis of anatomy alone, I would include in this 

 group Vallonia, StroMlops and probably Spelaeodiscus. 



ACANTHINULINAE. 



This group develops a weak shell with prominent epidermis, 

 which often develops riblets or projections. It may include 

 Acanthinula, Planogyra, Zoogenetes and Spermodea, although 

 the male genitalia of the last two have not yet been published. 



Recent anatomical descriptions of Acantlmiula aculeata 

 (Miill.) are those of Hesse (1915), Boycott (1917) and Steen- 

 berg (1917) ; Steenberg's figure of the genitalia (oviparous) 

 is reproduced (pi. 4, fig. 6). It has a spermatheca (be) of 

 the short type and a short vagina (va). Its penial appendix 

 is short, has a terminal sac (ap') and enters a basal swelling 

 (ap) which looks like the apex of the appendicular penial 

 arm in Planogyra. The epiphallar arm (pe') of the penis is 

 bifid apically, with the epiphallar (ep) entrance between the 

 two "diverticula " (di. di'), and with an insertion of the 

 penial retractor (re) on one of them. 



The female genitalia of Zoogenetes (ovoviviparous) are de- 

 scribed by Steenberg (1925) and those of Spermodea (ovipar- 



