40 University of Michigan 



the distal edge of the tooth to almost 1/3 of its depth ; laterad 

 to the cusps, fully half of the distal edge of the entire tooth 

 is undivided, slightly thickened and recurved. 



Animal : very dark in color, almost black ; foot very short, 

 almost circular; snout long; tentacles stout, clavate. 



Cistulops raveni arubana, new subspecies 



Type locality: (A2b) spur of Seroe Pretoe, between Roois 

 Spoki and Hundoe, Aruba. 



Distribution: Aruba, Eooi Frances, south to Seroe Pretoe 

 and east of Fontein (A2, 3). Infrequent to common; habitat 

 similar to raveni. 421 specimens collected. 



Shell : males about as large as females of raveni. Color : 

 typically albino, but more commonly as in raveni. Whorls : 

 ly^ in an entire male; 8% and 9 in, two entire females. 

 Last whorl : growth riblets commonly thinner and more widely 

 spaced than in raveni. Other characters as in raveni. 



Operculum: similar to raveni. 



Radula (fig. ix-26, no. 2) : very similar to raveni, but the 

 minor serrations of the central cusp of the inner lateral appear 

 somewhat heavier. 



Measurements 

 Shell Peristome Aperture Whorls 



alt. maj.diam. mill. diam. alt. diam. inside 



A2, male; complete 8.2 39(3.2) 33(2.7) 32(2.6) 100(2.6) 18(1.5) 71/2 

 female; entire 10.5 35(3.7) 31(3.2) 28(2.9) 104(3.0) 17(1.8) 8% 

 female (type) 11.1 33(3.7) 31(3.4) 26(2.9) 107(3.1) 16(1.8) 9 



A2. Quite common (407 specimens collected). 28 specimens are quite 

 unicolor, white to cream. The shells from the southern stations (A2a, b) 

 average even larger than the lot from A2c. 



A3c. Infrequent (14 specimens). 



Although all of the lots of typical raveni average noticeably 

 smaller than those of arubana, the two forms intergrade ex- 

 tensively. The much larger percentage of albinos (the typical 

 form) on Aruba also seems evidence of racial differentiation. 



