THE COOK'S OS HARVEY ISLANDS. 385 



They diffpr from the former genus in the total absence of laminae in the palate, 

 and, with very few exceptions, they are wanting on the parietal region. The 

 whorls. of all those species without parietal lamina increase in size more rapidly, 

 and the body whorl is broader, and the aperture less contracted than in Pitys. 



Patula jugosa and tenuicostata have a very close resemblance to the United 

 States Patula striatella. 



The rare occurrence of two or three species with parietal lamina connects the 

 genus with Pitys, and is one of the numerous instances of the difficulty experi- 

 enced in the attempt to separate the Helices into sharply-defined genera or sub- 

 genera. 



The Polynesian Patulce, yvhich. culminate in the southeastern groups, are gene- 

 rally diffused throughout the various islands in Polynesia. They have not, as yet, 

 been discovered in Micronesia; but, owing to their small size, dark color, and 

 habits of concealment, have probably escaped the notice of collectors. South of 

 the equator they range west as far as the Viti Islands, and, in all probability, are 

 diffused throughout Melanasia. A number of species are recorded from South 

 Australia and Tasmania. 



They are all strictly terrestrial, and are found lurking under rotten wood, 

 decaying leaves, and adhering to the under side of loose stones. 



P. TENUICOSTATA, Garrett. 



Pitys tenuicostata, Garr., Amer. Journ. Conch., 18T2, p. 229, PI. 12, fig. 23. 



Patula tenuicostata, Schmeltz, Cat. Mas. Godeff., v. p. 94. 



Helix tenuicostata, Pfeiflfer, Mon. Hel., viii. p. 547. __ 



This interesting shell cannot easily be confounded with any other South Poly- 

 nesian species. As compared with the Sandwich Island jugosa, which it more 

 nearly resembles than any other, it is not so large, the umbilicus smaller, the spire 

 more planulate, and the last whorl is broader. 



So far as known, it is peculiar to Rarotonga, and, though rather widely diffused 

 over the island, is comparatively rare. 



It may readily be distinguished by its uniform pale brownisli horn color, and 

 the thin rather distant radiating riblets. 



P. CANALis, Garrett. 



Pitys canalis, Garr., Amer. Journ. Conch., 1862, p. 22Y, PI. 19, fig. It 



Patula canalis, Schmeltz, Cat. Mus. Godeff., v. p. 93. 



Helix canalis, Pfeiffer, Mon. Hel, vii. p. 546. 



This well-marked species is also confined to Rarotonga, where we obtained a, 

 few examples in one valley only. 

 77 



