104 PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND. 
is either practically straight or slightly concave, in some it appears to 
be very slightly convex. Some variation in the ornament has also 
been noted. Although the riblets are generally wholly concentric 
about the apex of each valve, near the dorsal and ventral 
margin of some individuals they are arranged almost longitu- 
dinally. Their number and regularity also vary, and, if the 
number of reticulations joining them is great, the concentric 
arrangement may become rather confused. The size of all mature 
individuals of this species has been found to approximate to the 
dimensions given above for the holotype. The recent Ilyodromus is 
known to be a bottom dweller, creeping among the plants and in the 
mud of lake floors. It belongs to the subfamily Herpetocypridinae, all 
members of which are incapable of swimming in the adult state. Six 
species of the genus have been recorded from New South Wales, but 
only one species has been recorded as yet from Queensland (Henry, 1923) . 
The species has been named after the characteristic concentric ornamenta- 
tion of this little ostracod. 
Localities and Age : In The Narrows Tertiaries: Bores 1, 3, 4, 5, 6, 
12, 13, 14 (see species occurrence charts), parishes of Targinie and 
Bundle, county of Deas Thompson, between Gladstone and Bockhampton. 
This species has a vertical range of only 115 feet. In the Petrie Series: 
Houghton’s bore, at about 45 feet, portion 24, parish of Warner, county 
of Stanley, near Lawnton, between Brisbane and Petrie. The fact that 
this species has been found at only the one locality in the Petrie Series 
suggests that it is a moderately short-ranged form. Probably Miocene. 
Genus Erpetocypris Brady and Norman, 1889. 
Genotype: Erpetocypris reptans (Baird), 1850, p. 160. 
Diagnosis: Carapace in lateral view elongate. Height less than, or 
approximately equal to, one-half of length. Dorsal margin variously 
arched. Ventral margin sinuated in front of middle to almost straight. 
Valves rather unequal, left usually slightly larger than right. Surface 
of valves generally smooth, to punctate. 
Range: Oligoeene to Becent. 
Erpetocypris aequalis Chapman, 1935. Plate VI, fig. 3. 
Holotype: F. 7851, University of Queensland Collection. Locality: 
Gully on Portions 118, 119, 120, Parish of Bundamba, County of Stanley, 
about 5 miles S. of Goodna, Queensland. Geological Horizon : Bedbank 
Plains Series. 
Description: Carapace medium-sized, in lateral view elongate oval 
to subreniform, highest slightly in front of middle. Height approximately 
equal to, or slightly less than, one-half of length. Dorsal margin evenly 
and gently arched. Ventral margin nearly straight to slightly concave 
in median region. Anterior extremity broadly rounded, meeting ventral 
margin with moderately sharp angle. Posterior extremity well, but not 
so broadly, rounded. Valves moderately convex only, to rather com- 
pressed. Convexity fairly regular, and position of greatest thickness 
located slightly behind middle. Valves equal, or very nearly so. In 
profile acute ovate, with anterior extremity somewhat compressed and 
posterior roundly inflated. In end view oval. Surface of valves 
polished, smooth except for few scattered punctations. Seven muscle scars 
