1896.] NATURAL SCIENCES OF PHILADELPHIA. 403 



Narborough, from which no land shells have yet been collected, 

 has a rich and abundant vegetation with a luxuriant growth of man- 

 groves on the eastern shore. This island was the last to exhibit its 

 volcanic activity, and the fauna may prove meagre, yet it can hardly 

 be doubted that it will afford a certain number of species and pos- 

 sibly some novelties. 



The islets of the northeastern group are small and comparatively 

 barren. Tower and Bindloe are not high enough to profit much by 

 the mists. Abingdon is higher, and with Bindloe shows a certain 

 proportion of green. No land shells are known from Tower and 

 Abingdon. From Bindloe only the following are yet reported : 



Bidimulus Darwini, Auricula stagnalis, Pedipes angulatus. 



From the central group come : — Bidimulus Wolji, B. duncanus,^ 

 B. calvus, B. jacobi, B. jacobi var. cinereus, B. olla, B. Tanneri, 

 B. imifasciatus, B. Simrothi, B. n. sp., near to Habeli, B. rugiferus,'^ 

 B. Reibischi, B. nesioticus, Trochovioryha Bauri,^ Pupa clausal 

 Pupa Wolfii, Succinea Bettii, Succinea corbis, Leptinaria chatha- 

 mensis, Leptinaria sp. larger than chathamensis, Helicina nesiotica. 



In all 21 forms, of which none is common to the northeastern 

 group of islands ; 14 are peculiar or not yet reported from either 

 the northeastern or southeastern group of islands ; one is of doubt- 

 ful locality but provisionally placed here on account of its similar- 

 ity to B. rugiferus ; and the remaining six are common to the south- 

 eastern group. Onchidium is not counted. 



In the southeastern group are found thirty-three forms (not count- 

 ing Onchidium), of which the following are peculiar to, or not yet 

 found outside of this group of islands : — Bulimidus nux, B. achatelli- 

 nus, B. rugtdosus, B. nudus, B. planospira, B. ustidatus, B. eschari- 

 ferus and var. ventrosus, B. galapaganus, B. perspectivas, B. jacobi 

 var. aciduH, B. nueida, B. amastroides, B. curtus, B. Bauri, B, 

 canaliferus, B. chemnitzioides,B. Habeli, Vitrea chathamensis, Conulus 

 galapaganus, Succinea producta, S. brevior. 



To which may be added: — Melampus trilineatus, Tralia pana- 

 mensis, Williamia peltoides, Siphonaria gigas. 



Omitting the Auriculidce and Siphonariidce, we have as supposed 

 peculiar forms in each group of islands, twenty-one characteristic of 

 the southeastern, fourteen from the central and one from the north- 

 eastern group of islands, which agrees well with the hypothesis that 

 the species originated with forms brought by winds and currents 

 which impinge first on the southeastern group. 



