CENSUS OF THE OLDER TERTIARY FAUNA OF AUSTRALIA. 403 
several subgenera and sections, some of which are yet to be 
defined. 
Genus Cerithiopsis. 
CERITHIOPSIS MULDERI, spec. nov. 
Shell minute. Protoconch styliform of four slightly convex 
smooth whorls. Spire of four flat whorls, forming a cylindroid 
cone ; the ornament consists of two equidistant stout spiral ribs 
(sometimes a third small one at the posterior suture), nodulose at 
the intersection with weaker axial ribs. Suture linear, but 
apparently channelled by approximation of the adjacent spiral 
ribs. Last whorl with two nodulose ribs, a smooth rib at the 
basal angulation and two smooth slender ones on the base. Length 
of protoconch -3; length and breadth of spire 1:5 and -4 mm. 
Eocene, Fyansford (several examples). 
This species of a genus new to the Eocene fauna of Australia, 
as previous records belong to Vewtoniella, is named in compliment 
to Mr. Mulder, whose untiring researches among the minuter 
mollusca of the Geelong Eocenes, have yielded such large results: 
C. Mulderi resembles C. ridicula, Watson, recent in Southern 
Australia, but it has a longer protoconch, has two primary 
revolving ribs (instead of three) and has fewer ribs on the base. 
Family Rissorp#. 
Genus Ohileutomia, Tate and Cossmann, 1898. 
Etymology : Chilos, lip, eu, well, and tomos, a cut. 
Type: C. subvaricosa, Tate and Cossmann ; Eocene, Victoria. 
Shell conical, variced; embryo orthostrophe with an obtuse and 
oblique nucleus. Aperture expanding at the front, with a contin- 
uous thick peristome. Labrum notched at the inferior angle and 
varicosely thickened at the exterior. Columella slightly excavated ; 
columella-border callous, reflected and detached from the false 
umbilicus, 
Differs from Rissoina by the notched labrum, effuse and rounded 
front aperture, and by the umbilicus. Besides the type, there 
