TRUNCATELLINA. 59 



This genus of minute snails has a wide but apparently dis- 

 continuous distribution. It is found on the Atlantic Islands, 

 fossil only in Madeira, living in the Canaries and Cape 

 Verdes; throughout Europe except in the far north, and in 

 Asia eastward to the western Himalayas, with a remote out- 

 post in the central Loochoo Is. In Africa there is a herd in 

 the Abyssinian highlands, some scattered species in British 

 East Africa, and in South Africa it becomes abundant again. 

 Yet but little collecting of minutia? has been done in tropical 

 Africa, where the genus may have a greater range. 



The absence of inferior tentacles has been repeatedly ob- 

 served in Europe, for both toothless and tridentate species. 

 Mr. Burnup informs me that South African species he has 

 examined alive lack inferior tentacles. 



The blunt teeth, never more than three, with the columellar 

 lamella oval, axially lengthened instead of entering spirally, 

 are characteristic ; also the invariable deep immersion of the 

 palatal fold, from one-third to two-thirds of a whorl inward 

 from the lip. The teeth are rather more like those of Pupilla 

 than like other genera of Vertiginin<c. 



As in other land shells of cylindric shape, the length is 

 often quite variable, sometimes even in the same colony; the 

 diameter remaining more constant. In the writer's measure- 

 ments the diameter is measured to the edge of the lip ; more 

 conservative quantities would be obtained by measuring 

 above the aperture. 



Palaeontology of Truncatellino. 



The record begins in the Upper Oligocene of Germany and 

 northern Bohemia, with both smooth and rib-striate species 

 having teeth like the recent T. daustralis. Others followed in 

 the Miocene, and it will doubtless be turned up in the Plio- 

 cene of southern Europe. The earliest known forms appear 

 to be in the same stage of evolution as the Recent toothed 

 species. When really early stages of the genus are recovered, 

 they may be expected to possess angular and upper palatal 

 teeth also, with the palatals less immersed. The toothless 

 modern species are the most evolved of the genus. References 



