MUSEUM OF COMPARATIVE ZOOLOGY. 175 



species The animals of tlie arboreal species are lighter-colored than 



the terrestrial. The color of the animals in all the solid species varies 

 from a pale cinereous, through all the intermediate shades of black, to 

 dusky slate, while the thin-shelled species before mentioned are more or 

 less of a luteous color." * The shells of many species of Partula vary 

 in size, weight, and coloration. When numbers of these apparent vari- 

 eties are compared, aided by a microscopic examination of the surface of 

 the shell, their specific identity is obvious. Some Partulse may readily 

 be mistaken for small Bulimi, especially that division of the genus in 

 which the pillar tooth is absent, and the lip not broadly reflected, and 

 concave, as in P. rosea Brod. In other species the lip is widely re- 

 flected, thick, and flat, often with a large pillar tooth within, which 

 gives the aperture an auricular appearance, as seen in P. auricnlata 

 Brod., constituting two natural divisions of the genus, the Auriform and 

 Buliviiiioid, which are divisible into sub-groups. 



Partuhc diff'er from Bulimi in having the columella broadly reflected 

 and compressed at base, leaving an umbilicus of variable size, whilst a 

 few are imperforate, or narrowly umbilicate, and many species constantly 

 exhibit a small tubercle on the columella. The spiral strice of the sur- 

 flice together with the embryonic fovea of the apex of the shell are found 

 in all the species. Some species are constant in form and color, and also 

 in the presence or absence in the adult of a denticle on the columella 

 and a pillar tooth, whilst other species are more variable, especially as 

 regards the latter feature. In P. spadicea Eve., only one specimen in 

 fifty has a pillar tooth, while in others the tooth is not absent in several 

 hundred specimens. The same variation is observable in sinistral Par- 

 tulce. P. Mooreana nobis is both sinistral and dentate in fifteen hundred 

 examples. P. Otaheitana Brug. and varieties exhibit a majority of re- 

 versed examples, while P. vexillum Pse. has one in fifty and P. affinis 

 Pse. only shows one in several hundred.f 



In sinistral examples, the whorls are either excessively drawn out, as 

 in P. bulimoides Less., P. rubescens Rve., and P. perversa Pse. Mss. = 

 Otaheitana Brug.; or they are closely rolled together, as in P. crassa Pse. 

 Mss. and P. brevicula Pse. Mss. = P. Otaheitana vars. 



In the auriform division of the genus the lip of the immature shell 

 is at first concave, the outer margin in the early stages partaking of the 

 color of the epidermis. This concavity and coloration disappears as the 



* Garrett in htt. 



t I possess a sinistral example of Patula Cooperi W. G. Biun., from Colorado, se- 

 lected from bushels of dextral speciuiens. 



