AMASTRA, KAUAI. 145 



each whorl near the lower partition, and widest where it joins 

 the upper partition. Hence, until the shell is nearly mature 

 there is an umbilical orifice 'behind the reflexed columellar lip ; 

 in the last whorl this becomes closed. In the last half- whorl 

 a callous lamella is superposed upon the axis just above its 

 basal contraction. 



The shell is angular at the periphery in all post-embryonic 

 stages of growth, but in the third or fourth whorl a project- 

 ing periferal keel appears, persisting to the aperture and be- 

 coming stronger with age. In the adult stage the aperture 

 becomes smaller, especially narrower, than in shells younger 

 by a whorl. Finally, senility is marked by the descent of the 

 last whorl below the keel, and its further contraction laterally. 

 These stigmata appear earlier in some shells than in others. 



Pease collected this species at an elevation of about 4,500 ft. 

 'The animal is very small in comparison with the size and 

 thickness of the shell, a little larger than the diameter of the 

 latter, and excessively narrow. It drags the heavy shell bal- 

 anced on its back. When it crawls the head is stretched out 

 as far as possible, the two ends of the body solidly fixed, until 

 the middle part contracts and draws the shell forward. ' ' 



Section ARMIELLA Hyatt. 



At first sight this group appears to be obviously a modifica- 

 tion of Kauaia, having an additional carination along the 

 shoulder and a broad, flattened or concave zone evolved on 

 the outer side of the volutions between the carinae. But 

 closer obervation develops the fact that the young probably 

 resembles the young of Carelia, and then it is at once evident 

 that the volutions with their peculiar angulatious and obtuse 

 spire are similar to the most primitive forms of Carelia. 

 These are C. bicolor (pi. 16, fig. 7, neanic stage) and C. adusta, 

 which change the least during their development, and in their 

 ephebic stages are more like their own young than the more 

 elongated species of Carelia. The present group is, therefore, 

 regarded here as an offshoot of Carelia having a stouter spire 

 and more pronounced bicarinate volutions than any species 

 of Carelia. It is dedicated to Mrs. J. M. Arms Sheldon 

 (Hyatt, MS.). 



