178 BULLETIN OF THE 



number of denticles on the lingual membrane depends on the age of the 

 individual, I am not prepared to affirm. The shells, however, from which 

 my examples were taken were all mature, which is always indicated by 

 the thick, flat, and fully expanded lip. In the examination of the lin- 

 gual membranes, not only of Partula, but of all other Gasteropods, it is 

 noticeable that the denticles of the anterior extremity of the lingual 

 membrane are always more stout and prominent, gradually diminishing 

 in size towards the posterior part, where for several rows the denticles 

 become almost obsolete, presenting at last a mere rudimentary appear- 

 ance. In preparing a lingual membrane for a slide it may be observed 

 that the denticles at the anterior extremity always separate more read- 

 ily from the membrane. This, taken in connection with their gradual 

 diminution in size, has suggested the query in my mind whether the 

 wear and loss of the anterior denticles were supplied by a constant 

 renewal of those from behind. From the continued presence of rudi- 

 mentary denticles in varying stages of growth on the posterior part of 

 the lingual membrane of all Gasteropodous Mollushs, whether terrestrial, 

 fluviatile, or marine, which I have examined, it would seem probable 

 that the mode of growth is such as I have indicated. 



To Andrew Garrett, Esq., of Huaheine, who for many years has col- 

 lected in the various islands of the Pacific, I am under many obliga- 

 tions for specimens and information in reference to the stations and 

 distribution of Partulae, together with other facts of his personal ob- 

 servation embodied in this paper. To the Conchological Department of 

 the Museum of Comparative Zoology, so ably represented by Prof. 

 Charles E. Hamlin, I am indebted for the opportunity of examining the 

 collection of Partulee belonging to the late William Harper Pease, and 

 also for his kindness in selecting a suite from the duplicates in the 

 Museum. To the personal friendship of Professor Baird, seconded by his 

 efficient assistant, Professor Dall, I owe many thanks for the opportu- 

 nity afforded me of examining the collection of Partulffi contained in the 

 Smithsonian Institution. To Edgar A. Smith, F. Z. S., Assistant Con- 

 chologist in the British Museum, I am under obligations for his kindness 

 in comparing my specimens with types in the Museum, and for valuable 

 information pertaining to the same. 



For specimens I :tm indebted to many friends, among whom I may 

 mention A. D. Brown, Esq., of Princeton, New Jersey ; Robert Damon, 

 Esq., of Weymouth, England ; Mr. Robert F. Geale, formerly with Hugh 

 Cuming; G. B. Sowerby, Jr., Esq., of London; and I>r. Schmcltz, of 

 the Museum Qodeflroy, Hamburg. 



