8 PRONESOPUPA. 



This is the most widespread species of Pronesopupa in the 

 Hawaiian Islands, though it is not as frequently collected as 

 P. boettgeri or P. boettgeri spinigera. It is found under the 

 same conditions as these two forms, though more rarely taken 

 on stones or dead leaves. Fossil specimens have been found 

 in several recent deposits on Oahu, and two or three on 

 Hawaii. They are usually quite rare in any deposit. 



This species is easily recognized by its helicoid form. The 

 spine-like processes of the costse are extremely delicate and 

 are easily rubbed or broken off in handling the specimens. 

 These spines are longer and narrower than those of boettgeri 

 or its subspecies. In the large series of this species exam- 

 ined no specific or varietal differences were found in the 

 shells from the different islands. 



In the fossil specimens examined the costse are low, of a 

 uniform height, the processes having doubtless been broken off. 



In embryonic specimens of nearly two whorls from the 

 type lot, the shells are flat; the beginning of the first whorl 

 is immersed and the rest of this whorl hardly projecting 

 above the second whorl. The surface is granulose or punc- 

 tate, the minute granules being arranged in transverse rows, 

 gradually forming costae near the end of the second whorl. 



5. PRONESOPUPA BOETTGERI n. sp. PL 1, fig. 17. 



The shell is perforate (umbilicus small, circular, about % 

 the diameter of the shell), globosely conic, buckthorn brown, 

 costate; the costae delicate, thin, transparent, membranous, 

 forming on the last and penult whorls triangular tooth-like 

 processes, abrupt on the lower margin but above tapering 

 more gradually. Spire with convex outlines, the whorls very 

 convex, separated by a very deep suture. Whorls 4, the em- 

 bryonic whorls indistinctly punctate, the costae not appearing 

 until near the end of the second whorl. The last whorl is 

 very large, somewhat saccate, convex about the umbilicus, 

 ascending slightly near the aperture, with 26-30 costae, about 

 0.09 to 0.12 mm. apart, between the costae the surface is more 

 or less transversely minutely wrinkled. Aperture oblique, 

 broad, truncate-ovate, slightly flattened on the dextral side, 



