BY W. F. PETTERD. 



except its diminutive size and rounded whorls, in both of 

 which it appears to be very constant. At some future time I 

 hope to be able to describe the animal with the dentition, 

 not only of this, but also of other species that I have named. 



POTAMOPYEGUS (?) MARGINATA. 71. Sp. 



Plate I. Fig. 0. 



Shell, small, elongately conical, thin, almost smooth, whitish 

 horn colour, somewhat glossy. Whorls, 5| to 6, scarcely 

 rounded, margined with a fine line above the sutures, apex 

 very obtuse and mammillated. Aperture, small, ovate a little 

 expanded below, peristome continuous, attached to the body- 

 whorl. Operculum, horny, thin, pancispiral. 



Length, 4 ; hreadth, 1^ mill. 



Habitat — a small trickling stream near the Heazlewood 

 Kiver, which is tributary of the Whytc. 



I have no hesitation in describing this, in some respects* 

 remarkable little shell as quite a new form, as will be seen by 

 the figure ; it differs widely from all its congeners. The 

 sutural line and mammillate apex are peculiar to it, and it 

 alone. It was collected rather sparingly attached to small 

 stones and decaying leaves in a scarcely noticeable little 

 stream. 



Beddomeia. nexo suh-genus. 



Shell, globosely conical, thin, umbilicate, or sub-umbilicate. 

 Spire, short. Body-ichorl, inflated. Aperture, ovate, columellar 

 margin more or less thickened. Operculum, horny, paucispiral. 

 Ani>nal, with a somewhat broad foot, tentacles long, slender, 

 and pointed, eyes sessile at outer base of same, muzzle broad 

 and projecting. 



Dentition as in Potavwpyrgus, but the trapezoidal median 

 tooth has quite a different arrangement of the inferior basal 

 row, which consists of two ovate elevations on either side of 

 a curved central tooth 



Formula of denticles on median tooth -^ — - — ^ 



This new sub-genus it is necessary to form for the reception 

 of the globosely conical forms of Potainopyrcjus, which also 

 show the above-mentioned modification of the formula of 

 the denticles on the median tooth. 



I have named it in honour of my esteemed friend, Mr. C. 

 E. Bcddomc, the well known couchologist. 



