Genera Geotliaunia and Gjro.sti'opha. 2S5 



0. Hosei of Godwin-Austen. In addition to these 1 liave 

 just described five other species from the same island. 



A careful study of all these species seems to prove that the 

 genus Geothauma is not required, at all events at present. 



The form is sometimes as " pupiform " as in the Indian 

 species, e. g. 0. haritense, Smith ; the last whorl in 0. basa- 

 nense^ Smith, ascends and presses against the penultimate, 

 and the sculpture varies from the finest lamellae, as in 0. hari- 

 tense and 0. Wallacei, to much stronger lamellations, as in 

 O.jucundum, Smith. In 0. pulchellum the lamella are pro- 

 duced at the middle of the whorls, occasionally forming hollow 

 spine-like projections. In 0. Everettij Smith, these produc- 

 tions are still more developed, and in 0. mirabile, Smith, 

 they are as remarkable as in 0. grandlspinosum. 



The height to which the last whorl may be produced 

 upward is also a matter of degree. For instance, in 0. Hosei 

 and Everetti it rises almost as high as the top of the spire, 

 whereas in 0. haritense it does not ascend beyond the penul- 

 timate whorl. Most conchologists would at a glance confess 

 that these ten species from Borneo are evidently modifications 

 of one type ; and, even supposing that they differed materially 

 from the Indian forms, which is not the case, a new generic 

 name was not required for them. 



In 1865 Mr. H. Adams* described the genus Plectostoma 

 for the 0. de Crespignyi^ and this, as it does not appear to 

 have been preoccupied in any other branch of zoology, is still 

 available. However, until some distinguishing differences 

 are discovered in the anatomy of the animals, it seems to me 

 altogether impossible with reason to separate the Indian and 

 Bornean species on conchological grounds f- 



In my opinion the genus or subgenus Gyrostropha is 

 equally useless. It was suggested by M. AnceyJ to include 

 . pauluccice , Crosse and Nevill, and 0. perakensis, Godwin- 

 Austen and Nevill, from Perak. He considered that they 

 should be separated from the typical Indian forms, because 

 the summit of the spire was supposed to be roundly obtuse or 

 subglobose and the aperture situated almost in a vertical 

 plane parallel to the axis. Can anything be more trivial than 

 this? We might as w^ell separate generically shells having 

 but five instead of five and a half volutions ! 



* Aun. & Ma«'. Nat. Hist. 1865, vol. xv. p. 177. 



t Mr. W. T. I31auford has already expressed a similar opiuion (Ann. k 

 Wag. Nat. Hist. 1867, vol. xix. pp. 305, 306). 

 X Bull. Soc. Mai. France, 1887, p. 275. 



Ann. & May. N. Hist. Ser. 6. Vo/. xi. 21 



