126 Annals of the South African Museum. 



ureter seems to have been developed, though further information is 

 needed about the palhal organs of these snails. On the other hand, 

 the fine striae on the jaw are retained in Pedinogyra and Anoglyjjta, 

 and the vas deferens is still partially embedded in the wall of the 

 penis in the latter genus. Moreover, the lip of the shell is unusually 

 simple in this subfamily, the appendiculum is well developed, and 

 the egg, though large, does not attain the enormous size found in 

 some of the more highly specialized members of Acavidae. The 

 penial retractor arises from the columellar muscle, or from far back 

 on the floor of the lung, instead of near the front. 



Hedley, to whom we owe so much of our knowledge of these 

 snails, was the first to demonstrate that the Australian genera 

 Hedley ella,''' Caryodes, Anoglypta, and Pedinogyra, were related to 

 one another, notwithstanding their striking external differences.! 

 Semper had already remarked on the resemblance of Hedleyella to 

 Acavus and Helicophanta from Ceylon and Madagascar,:]: but after 

 comparing the anatomy of Hedleyella and Caryodes with that of 

 Acavus, Helicophanta, and Ampelita, Pilsbry states that the relation- 

 ship between the xlustralian and Indo-Madecassine genera is by no 

 means intimate §. The Australian region has long been cut off from 

 the other three areas in which the Acavidae are found, and contains 

 a separate branch of the family, less primitive in some respects than 

 the Strophocheilinae, but not so highly organized as Acavus and its 

 allies. This subfamily may be named the Caryodinae. 



The region extending from the south of Madagascar to the south- 

 western part of the peninsula of India remained a single large 

 island, or a closely connected chain of islands, long after it was 

 separated from the Australian region on the east and South Africa 

 on the west ; and it was probably not until Tertiary times that a 

 series of faults, accompanied by subsidence, sent the greater part of 

 that land beneath the Indian Ocean. The genera Acavus found in 

 Ceylon, Stylodonta in the Seychelles, and Helicophanta and 

 Ampelita in Madagascar, must therefore be regarded as the 

 surviving remnants of a group which formerly also inhabited the 

 intervening areas. 



This group is that which lies nearest to the original centre of 

 evolution of the family, and accordingly it includes the most highly 



* Hedleyella, Iredale, 1914 (Proc. Mai. Soc, xi. p. 174)=Prt»rf«, Albers, 1860, 

 nee van Heyden, 1826. 



t Eec. Australian Mus., 1892, ii. p. 29. 



\ Eeis. iin Archip. Philippin., 1873, iii. p. 104. 



§ Man. Conch., 1895, ix. p. 164. 



