50 
Ton Ihedale. 
fresh (“ondition the surfae<' is eoveied with a thin, shortly ])ilosc e))idermis. 
Worn shells exhibit iiuiumeTablc minute ])unctures showing: where the short 
delieate setae have been. Whorls TVo, regularly and rather slowly increasing, 
moderately convex, and separated by a deep sutural Hue, besides tlu‘ punc- 
tures, exhibiting tine lines of growth; last whorl I'ouuded at the jieriphery, 
only very leebly dellexed close to the aperture, and exhibiting a slight depres- 
sion above about the middle of the uijper inargi)! of the ]ieristome. Aperture 
somewhat triangular in outline, but with rounded angles, almost horizontal 
in position; peristome narrowly relleetcd above, more broadly expanded along 
the basal margin, espieeially over the umbilicus. A conspicuous tubercle er 
prominence occurs on the innin- edge of the basal margin, and a less pro- 
nounced one within the upper margin correspiondiiig to the slight depression 
upon the outer surface of the whorl. Breadth 10 mm.; height 4 mm.” 
Genus WESTEALTRACHIA tredale 1933. 
1938 — Westraltracliid Iredale, Hoc. Austr. IVIus., Vol. XIX, ]). 55, xAug. 2. 
Orthotype Trachitt froggatti Ancey. 
This geiiei'ie name was intrf)duced for a uundoer of species, which Ancey 
had, with great doubt, referred to Tracliia. The species are flattened helicoids 
with low spires and keeled or subkecled periphery, narrow umbilicus and trans- 
verse mouth sometimes basally flattened and indi.stinetly toothed. Although 
generally smooth and shining, the tj'pe is granulose and dull, and it may bo 
that the smooth sjiecies should constitute a separate snhgenns, which may 
be called Zygotrachia the species, 11'. alterna. being named as type. 
Westraltrachia froggatti Ancey 1898. 
Plate 111., fig. 10. 
1898 — Tracliia froggatti Ancey, Proc. Limn Soc. X.S.W., Vol. XXII., p. 774, 
pi. XXXA'I., lig. 2, June 4. Oscar Hange, 100 miles inland from 
Derby, North-West Australia. (W. W. Proggatl). 
Slndl small, sidjconical, deiiressed, stout, spire a little devated, wdiorls | 
flattened, sutures little impressed, last whorl acutely keeled, mouth oblique, 
outer lip expanded and a little recurved. A))ex radially finely subgranose, 
adult sculpture flattened coarse granulation finer on the base. 
Westraltrachia derbyi Cox 1892. 
Plate III., fig. 6. 
1892 — TTrlix [lladra) derhyi Cox, Proc. Linn. Roc. N.R.W., Rev. 2, A'ol. VI., 
p. 56(1, pi. XX.. figs. 4, 5, I\Iay 2:1, Derby District, North-West 
Aiisiralia (W. W. Proggatt). 
1894 — ihdix (Tracliia) dcrbyaiia Rmith, Proc. Malac. Roc. (Lond.), Vol. I., 
]). 92, id. VTI., fig. 19. .tune. Burner (error pro Barrier) Ranges, 
Derby, X(n-lli-West Australia. 
Shell .small, snbdiscoidnl, spire a little elevated, whorls little rounded, 
sutures impressed, urabilieatc, umbilicus narrow, deep, columella reflected, 
mouth open, outer lip. a little reflected with a slight snlmodulation on base. 
Coloration whitish marbled with brown flames above, a post peripheral 
brown band, rest of base dirty white, shell shining. Apex smooth, adult 
sculpture faint growth lines only. Breadth 11 mm.; height 6 mm. Collected 
on the Barrier (— Nainer) Range by W. W. Proggatt. 
