1888.] NATURAL SCIENCE^ OF PHILADELPHIA. 17 



tween Achatinella and Leptachatina, the latter has received especial 

 attention in the preparation of this paper, and for the present it has 

 been retained in the genus Achatinella. In analyzing the species 

 of Leptachatina proposed by Dr. Gould, of which L. acuminata Gld. 

 was designated as the type, they are found to be divisible into three 

 groups. In the first may be placed the elongate or cylindrical and 

 semi-transparent varieties, as L. acuminata, striatula and cerealis 

 Gould, gracilis PfeifFer, tenebrosa Pease, terehralis and exilis Gul., 

 and /tfsca Newc. In the second, the short oval clear and polished va- 

 rieties, as cingula Migh. saccata Hartm. brevicula Pse. and nitida 

 Newc. And in the third, the larger inflated and more stout species, as 

 Sartmanii Newc. M. S. sacclncta, Jumosa, and vitrea Newc, fusca and 

 resinw/a Gul. together with corneola and pyramis Pfr. The major 

 part of the species are terrestrial in their habits, while a few are 

 arboreal. In my examination of the Achatinellse, I have also inclu- 

 ded the allied genus Aurmilella. The generic name of Achatinella 

 has been used by all authors previous to Dr. Pfeiffer's sub-division 

 of the genus in Malakozocilogische Blatter in 1854 and 1856. Owing 

 to several causes the species have been burthened with numerous 

 synonyms, many of which have been hei-ein omitted, to avoid a 

 needless repetition of names. Their variability in form, age and 

 color, has misled naturalists into the error of multiplying the spe- 

 cies, and a change of environment Dr. Newcomb informs us, is 

 known to so alter the appearance of some, as to cause them to be 

 mistaken for distinct species. A change of environment and mal- 

 nutrition materially modifies the growth of all animals, and no- 

 where is it more observable than in the molluscan fauna. The 

 diflferent appearance of depauperized or aberrant forms of shells is a 

 prolific source of error, and often of embarrassment to the student of 

 natural history, since corrections can only be made by the examin- 

 ation of types in scattered collections. Mr. Geo. W. Tryon Jr. in 

 Ms recent books on conchology, has relegated to synonymy many 

 shells heretofore considered of specific value, some of which are 

 doubtless the result of environment or hybridization. In the early 

 history of the genus Achatinella, naturalists in different parts of the 

 world were engaged at the same time in describing the species, and 

 some of the names then given have only been established by priority 

 of publication. The application of boiling water to remove the an- 

 imal, materially alters the color of the shell, changing a green or 

 bright green to a dirty yellow ; and the manufacture of species by 



