PRONESOPUPA HYSTRICELLA The shell is perforate (umbilicus small, circular, open, deep, largely covered by the dilated columellar lip), helicoid, clay color, thin, subtranslucent, conspicuously costate; the riblets delicate, thin, transparent, membranous, forming on the last and penult whorls, just above the periphery, delicate, flat spines. Spire depressed, with slightly convex outlines and obtuse apex, the whorls very convex and separated by a deep suture. Whorls 4, the embryonic 1 whorls finely and closely granulose, the granules more or less arranged in transverse rows, gradually forming riblets towards the end of the second whorl, the last two whorls being strongly costate; the last whorl very large, depressed, convex around the umbilicus, slightly descending near the aperture, furnished with 28-30 costæ, about 0.2 mm. apart, the intercostal surface being more or less evenly minutely wrinkled. Aperture large, oblique, truncate-ovate, slightly flattened on the right side, forming a blunt angle at the shoulder, toothless. The outer edge of the peristome is slightly expanded, thin; the colu- mellar margin broadly dilated above the columella. Length 1.65, diam. 1.6, aperture, greatest length 0.92 mm. Length 1.5, diam. 1.7 mm. Hawaii Hilo, Reed's Island (type loc.); Holotype 11032 Bishop Museum, Paratypes 23233 Bishop Museum and A. N. S. P. Kauai, a single specimen; Oahu, common; Molokai, not rare; Lanai, a single young specimen, doubtfully reported to this species; W. Maui, not rare; E. Maui, rather common; Hawaii, common. 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 spinelike processes of the costæ 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 examined no specific or varietal differences were found in the shells from the different islands. In the fossil specimens examined the costæ 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 pune- tate, the minute granules being arranged in transverse rows, gradually forming costæ near the end of the second whorl.