192 



mented with close set, depressed, annular ridges, barely visible 

 by the unaided eye. 



Dimensions. — Length, 74; diameter of anterior aperture, 65 

 millimetres. 



Locality. — Muddy Creek. 



Entalis acriculum, spec. nov. Plate xx., fig. 11. 



Shell thin, subulate, very slightly curved, smooth, polished ; 

 marked with annular striae (visible under a lens) ; oral aper- 

 ture circular ; posterior aperture with a longish, linear fissure. 



Dimensions. — Length, 33 ; diameter of anterior aperture, 2'5- 

 millimetres. 



Locality. — Lower beds at Muddy Creek. 



GrEXTJS DeNTALITTM. 

 SYNOPSIS OF THE SPECIES. 



Longitudinally six to eight sulcated. D. aratum. 



Longitudinally ribbed posteriorly, smooth anteriorly. 



D. (?) bifrons. 



Without longitudinal ornament ; round, stout. D. lacteum. 



Trigonal, slender. D. (?) triquetrum. 



Dentalium aratum, spec. nov. Plate xx., fig. 8. 



Shell small, slightly curved ; acutely regularly 6 to 8 

 angled (usually 8) ; interspaces concave with a few slender 

 longitudinal riblets and striae, and close-set, fine, transverse 

 striations. 



The ornament varies in the acuteness and strength of the 

 ribs, and therefore in the depth of the interspaces ; in some 

 specimens, by reduction in volume of the primary ribs and the 

 increased size of the intermediate ones, the anterior part is 

 subrotund and multicostaced. 



Dimensions. — Length, 20 ; diameter of anterior aperture, 2 

 millimetres. 



Localities. — Gastropod bed of the River Murray Cliffs near 

 Morgan ; lower beds at Muddy Creek ; blue clays at Schnapper 

 Point ; Muloowurtie yellow clays near Ardrossan. 



D. nanum, Hutton, is similar to this species, but its ribs vary 

 from 8 to 13, and the interspaces are smooth. 



Dentalium (?) bifrons, spec. nov. Plate xx., fig. 5. 



Shell thin, round, nearly straight, posteriorly longitudinally 

 ribbed, anteriorly smooth. 



The ribs are slightly elevated, subangular, about 40 in 

 number, sometimes they are alternately stout and slender, be- 

 coming more depressed, and finally disappearing at about one- 

 third the total length from the apex ; the anterior portion is- 



