10 PRONESOPUPA. 



A more common form and one not found in pure colonies has 

 only the parietal lamella developed. The most abundant 

 form is the one selected as the type with both an angle and 

 parietal lamellas. The angle lamella is present as a very low, 

 indistinct knob, usually slightly separated from the termina- 

 tion of the outer lip. The parietal lamella is about twice as 

 long as its height. In nearly adult specimens the parietal 

 develops before the angle lamella, the latter never appear- 

 ing except in fully adult specimens. In most adult speci- 

 mens there is a slight swelling on the inner margin of the 

 columella, which does not appear to develop into a well- 

 defined lamella. 



In the embryonic shell of 1% whorls the early part of the 

 first whorl is immersed, the surface is rather strongly punc- 

 tate. The points are arranged in rather wavy, transverse 

 rows. The surface of this species is more strongly punctate 

 than that of embryonic specimens of acanthimda. 



From acanthinula it is easily separated by the closer, 

 spine-bearing eostae and the minute parietal and angular 

 lamella?. 



6. P. b. spinigera n. subsp. PL 1, fig. 11. 



The shell is similar to that of P. boettgeri but smaller and 

 without any teeth in the parietal wall. Length 1.41, diam. 

 1.2, aperture (diag.) 0.73 mm. Holotype 11031 Bishop Mu- 

 seum, paratypes 15319 Bishop Museum and A. N. S. P. 



This is by far the most abundant form of Pronesopupa on 

 the Hawaiian Islands. Several large series are in the Bishop 

 Museum collection, from Kauai, Oahu, Molokai, W. Maui and 

 Hawaii. Up to the present time no specimens have been seen 

 from E. Maui, Lanai, Kahoolawe or Niihau. It is probably 

 common in the first two of these islands but does not seem to 

 have been collected. It is very common under conditions 

 similar to those under which boettgeri is found. It is, how- 

 ever, much more abundant and is found more often existing 

 as pure colonies. It is easily recognized by its smaller size 

 and the absence of lamellae in the aperture. 



Embryos taken from specimens from Makiki, Oahu, have a 



