Occasional Papers of the Museum of Zoology 93 



Aperture formation in Brachypodella appears to be 

 hastened by injury and specimens with peculiarly distorted 

 peristomes are not uncommon. In the present subspecies, 

 quite a number of the specimens, although apparently unin- 

 jured, are almost perfectly conical, with the last whorl well 

 rounded and larger than any of the preceding ones ; a single 

 specimen (fig. xvii-72) also has the peristome adnate to the 

 last whorl. 



Brachypodella raveni arubana, new subspecies, 

 and form sinistrorsa, new 



Type locality: (A2b) Seroe Pretoe, between Koois Hundoe 

 and Spoki, Aruba. 



Distribution: Aruba, under limestone rocks. All of the 

 specimens from A2, and A3, and '93 per cent, of the 105 shells 

 from A4 are dextral (typical form) ; 7 per cent, of those from 

 Seroe Canashito (A4), and all from the shore-cliffs between 

 Perkietenboseh and Kralendijk (A5, quite rare) are sinistral 

 (form sinistrorsa). 



Shell (xvii-70) : similar in size to raveni, but usually more 

 cylindric ; greatest diameter usually above the 3rd whorl ; sur- 

 face more highly polished. Whorls: 14^ (in a medium-sized 

 specimen), of which about 10 are usually retained; later 

 whorls less convex than in typical raveni ; carina and periph- 

 eral emargination carried much higher on the shell. Growth- 

 riblets of last whorl: usually closely-spaced, but much lower 

 and more rounded than in raveni; carinal crests poorly de- 

 veloped or absent. Peristome: reflection broader than in 

 raveni. 



Radula and jaw: similar to raveni, but the intermediate 

 cusps of the central tooth are usually smaller. 



Measurements 

 Shell Spire Aperture Whorls 



alt. maj. diam, maj. diam. alt. diam. 



A4, complete 8.85 24(2.39) 22(1.99) 18(1.59) 107(1.70) 14^^ 

 A2, type, larg- 

 est (fig. 70) 8.32 32(2.67) 26(2.19) 21(1.75) 101(1.76) 8 



