104 PARTULINA, SECTION 3ALDWINIA. 



men ted in this way with the three species here mentioned, 

 removing perhaps a hundred individuals, old and young, 

 from an altitude of between 1,600 and 3,000 feet to about 800 

 feet above and near the sea, where they were placed upon a 

 magnolia tree. The chances of the colony surviving such a 

 complete change of environment seemed very small. Never- 

 theless for a short time the shells seemed to thrive, but they 

 were discovered by rats and the colony was soon exterminated. 



" Great numbers of Achatinellas, as well as Succineas, in 

 their natural habitat on the several islands are destroyed by 

 rats and mice, and the extermination of many of the species 

 is now being hastened by these agencies. 



" An Achatinella which Mr. D. D. Baldwin refers to Par- 

 tulina physa (=s confusa) was found by the writer abun- 

 dantly in the semi-fossil deposits closely adjoining the colony 

 of that shell above described. The great size of this fossil 

 leads to a first impression of its distinctness from confusa, 

 but a careful comparison of many specimens constrains the 

 writer to adopt Mr. Baldwin's view, since, as remarked by 

 that veteran conchologist, a description of the fossil would 

 read precisely like that of confusa save in respect of size. 



" Tables are appended which indicate the degree of pro- 

 lificness of the species here treated of. The season when the 

 shells were collected (January- April) was unusually cold and 

 stormy, and perhaps in mid-summer different ratios might 

 be had, although Mr. Thaanum. who has dissected many Oahu 

 species with reference to the number of young, tells me that 

 he has never noted much if any seasonal difference in this 

 respect, the shells bearing young the year round. 



' In several of the forms the number of shells examined is 

 too small to give results of much value. In the case of the 

 brown- whorled Iwrneri, for instance, a greater number would 

 doubtless materially reduce the average number of young 

 per adult shell. ' ' 



