AURICULELLA, OAHU. 75 



5. Shell dextral. turritella, no. 13. 



ft 1 . Shell sinistral. 



c. Parietal lamella minutely spinose. 



serrula, no. 14. 

 c 1 . Parietal lamella smooth. 



d. Length 8 mm., with 8 whorls. 



* castanea, no. 15. 



d l . Length 6.3 mm., with 8 whorls. 



petitiana, no. 16. 



Three species described by Pfeiffer, A. amcena, A. cham- 

 issoi and A. petitiana, have not been recognized with certainty 

 by modern collectors. It is not known positively that the last 

 two are from Oahu. 



Group of A. auricula. 



The shell is usually solid, rarely translucent, perforate, or 

 rarely imperf orate (when imperf orate, the umbilicus is closed 

 with the thickening of the columellar lip). The oblique diam- 

 eter is about half or more than half of the length. Spire conic 

 or a little convexly conic, composed of flattened or but slightly 

 convex whorls. Columella usually unidentate, often with 

 posterior minute fold deep within. Lip usually thickened, 

 expanded, sometimes duplicate, rarely thin. In the young 

 the shell is imperf orate, angulate at the periphery; without 

 palatal plicae, the columellar fold strong, nearly transverse, 

 with an acute edge. 



This group comprises the bright-colored or white species, 

 and a few with dull coloring. The shells are larger than in 

 the group of A. perpusilla, with more whorls, which are 

 nearly flat. 



The two Waianaean species, malleata and ambusta, are 

 well characterized, and in the East, A. diaphana is unmis- 

 takably distinct, also A. straminea, which however stands near 

 auricula. The rest of the species A. auricula, olivacea, man- 

 tana, amcena and pulchra form a complex of interrelated 

 forms in which * ' species ' ' are distinguished with difficulty. 

 The distinction made in the key between species with ' ' dupli- 

 cate ? ' lip and those with it 1 1 blunt, not duplicate ' ' is rather 



