20 Rev. T. Hincks on the 



appears almost circular, peristome not raised, sometimes a 

 thickened granulous border surrounding the orifice in front. 

 A vicularia none. Ocecium (?) . 



Dolomite Narrows, on shell. 



The oral sinus in this species takes its origin immediately 

 below the denticles on which the opercular valve works, and 

 is somewhat difficult to recognize. At first siglit the orifice 

 seems to be circular, as the sinus occupies nearly the whole 

 of the inferior margin. The lower cell in the figure (PI. XVII. 

 fig. G), Avhich is represented with the operculum in situ, is 

 defective in not showing the contraction below the denticles. 



We have here, we may suppose, one of the primitive forms 

 of the sinuated orifice, from which others may have been de- 

 rived by contraction (more or less) or other modification of 

 the marginal curve. The suboral pore of certain genera pro- 

 bably owes its origin to the isolation of the most specialized 

 form of sinus, a central notch with contracted aperture. 



Schizoporella maculosa, n. sp. 



Zooecia quincuncial, rather small, moderately convex, su- 

 tures shallow ; surface shining, covered with small punctures, 

 which are closed in by a brownish membrane, and give a 

 spotted appearance to the front wall ; orifice arched above, 

 with a shallow bluntly pointed sinus below, not contracted at 

 the opening, peristome slightly thickened ; on one side, just 

 below the orifice (or occasionally on both sides), a small 

 rounded avicularium on a prominent boss. Ocecium (?). 



On shell. 



The specimens of this form have unfortunately been mis- 

 laid ; but I hope to be able to give a figure of it in a subsequent 

 portion of the Report. 



Schizoporella Dawsoni, n. sp. 



Zooecia ovate, or hexagonal, quincuncial, depressed or very 

 moderately convex, separated by raised lines, highly calcified 

 vitreous ; surface reticulato-punctate (punctures appearing as 

 deep shafts in the vitreous crust) j orifice arched above, much 

 broader than high (narrow between the upper and inferior 

 margins), a shallow rounded sinus in the centre of the lower 

 margin, not contracted at the opening ; peristome not raised 

 thickened round the sinus. Avicularia none. Ocecium 

 rounded, closely united to the cell above, somewhat depressed 

 in front, glossy, covered with rather large punctures j a pro- 

 minent thickened border round the opening. 



Virago Sound, on shell. 



