390 



THE TERRESTRIAL MOLLUSCA INHABITING 



Mr. Pease's first description, which is copied by Dr. Pfeiffer, is not so accurate 

 as the second one published in the " Proceedings of the Zoological Society." It 

 is remarkable that the former author should have compared this species with 

 Jacquinot's rotula, which is described as a smooth, horn-colored shell, which Dr. 

 Pfeiffer refers to the section or subgenus Microcystis. Judging from Anton's 

 description of Oparica, though quite distinct, it is the nearest allied species. 



P. ROTELLINA, Pcase. 



Pithys rotellina, Pease, Jour, de Conch., 1810, p. 393. 

 Pitys rotellina, Pease, Proc. Zool. Soc, ISU, p. 453, 414. 

 Helix rotellina, Pfeiffer, Mon. Hel., vii. p. 262. 



Like the preceding species, this is also peculiar to Aitutaki, and is nearly 

 equally as abundant, both of which occur in forests near the sea-shore. It is the 

 smallest known Polynesian species, and could easily be mistaken for the young of 

 imperforata. It is, however, only half the size of that species, and the umbilicus 

 though small is pervious, and the striae are so firm and crowded as to impart a 

 velvety appearance to the surface of the shell. 



Of Mr. Pease's two descriptions, the one in the " Proceedings of the Zoological 

 Society" is the most correct, though Dr. Pfeiffer, as in the preceding species, has 

 copied the first. I cannot understand how Mr. Pease could have overlooked the 

 laminee in the palate, of which there are three or four, and most generally raised 

 striae on the wall of the aperture. 



P. Rarotongensis, Pease. 



Pithys Boratongensis, Pease, Jour, de Conch., 18t0, p 395. 



P%s iJoraionyensis, Pease, Proc. Zool. Soc, 1871, p. 453, 474. 



Helix Boratongensis, Pfeiffer, Mon. Hel., vii. p. 257. 



I collected Mr. Pease's type specimens at Atiu, not Rarotonga as stated by the 



above author. 



As in the two preceding species. Pease's first diagnosis, which is reproduced 

 by Dr. Pfeiffer, is not very satisfactory. The second one (1. c.) is very correct as 

 regards shape, sculpture, and number of internal laminae. 



The nearest allied species is P. De Gagei, inhabiting one of the Austral 

 Islands ; but that species has twice the number of laminae. 



GENUS LIBERA, n. g. 

 Shell small, widely umbilicated, umbilicus (in adults) strongly constricted so 

 as to form a cavernous or pouch-like cavity; whorls 7-9, costulate or striate, last 

 one angulate or carinate, rarely rounded; aperture subrhomboidal or securiform; 



