THE COOK'S OR HARYEY ISLANDS. 401 



but, owing to their diminutive size and dark color, are not easily detected in the 

 gloomy forests, unless especially sought for. They occur beneath rotten wood, but 

 more frequently in the cells and fissures of basaltic rocks, and range from the low- 

 land forests to over two thousand feet above sea level. 



Dr. Gould's type specimens were collected at Tahiti, where I also gathered 

 numerous examples, as well as at Huahine, Borabora, and Maupiti, in the same 

 group. Dr. Graffe found it at the Viti Islands, and Paetel records it from Samao. 



Mr. Pease's type specimens of armata were collected by me at Borabora, and 

 his dentifera I found in forests near the sea-shore at Aitutaki, not " Rarotonga." 



Zelebor's Dunkeri, which is very accurately described, was obtained at Tahiti, 

 during the voyage of the "Novara," and, together with Mr. Pease's two species, are 

 identically the same as ^a?^f^7/a, which is subject to considerable variation. 



In shape they vary from an abbreviate-ovate to oblong-oval, and still more so 

 in the relative proportion of the whorls. Some have them slowly and regularly 

 increasing, giving the outlines a subcylindrical form. Others have the two last 

 whorls abruptly enlarged, and both of the same diameter, whilst some have the 

 penultimate exceeding in diameter the body whorl. 



The color is pale corneous under a brownish, more or less distinctly shagreened 

 epidermis, which, in perfect examples, is furnished with distant oblique, deciduous, 

 membranous ribs, which, when viewed laterally, are frequently whitish, as men- 

 tioned by Pease in his description of armata. 



The last whorl, behind the peristome, is more or less conspicuously bisulcate 

 in the majority of specimens. The lip, which is darker colored than the epidermis, 

 is usually emarginate near the suture, and in old examples is thick and flat. 



They vary considerably in the number of teeth in the aperture. There are two 

 on the parietal region, which are elongate, more or less curved, and one is fre- 

 quently united to the outer lip. Sometimes there exists a third and smaller one 

 more deeply seated near the columella. The teeth in the palate vary the same as 

 in pediculus. 



GENUS SUCCINEA, Draparnaud. 



S. cosTULATA, Pease. 



%uccinea costulata, Pease, Proc. Zool. Soc, 1864, p. 611; 1811, p. 412. Pfeiffer, Mon. Hel., v., p. 



31 ; vii., p. 40. 



I found two examples of this well-marked species in a lot of land shells col- 

 lected for me at Aitutaki. They were the only specimens of the genus obtained 

 whilst exploring the group, and difi"ered none from Tahitian examples. 



Its small size, abbreviate form, and plicate striae are its most obvious characters. 



79 



