196 
K.J. McNamara 
large; food grooves short and weakly developed, 
extending less than a quarter the distance from the 
persitome to the ambitus. Periproct situated less 
than twice its diameter from posterior margin, 
except in very large specimens. 
Description 
Test small, reaching up to 44 mm test length (TL); 
ovate, with a thick, broadly rounded ambitus; 
posterior margin (interambularum 5) transverse; 
margins of ambulacra I and II and interambulacra 
1 and 4 also straight, intersecting each other with 
sharp angle; margin anterior of interambulacra 1 
and 4 broadly rounded. Test low, being highest at 
mid-test length at apical system; height 13-22%TL; 
rarely, in large specimens, as narrow as 77%TL; 
juveniles almost flat with relatively thinner margin; 
at margin test height varies between 10-20%; test 
longer than wide, width ranging between 84- 
92%TL; wider in small individuals, narrowing with 
increase in test size. Aboral surface rises slightly 
from lateral margin. Apical system slightly anterior 
of centre; tuberculate, with four gonopores. Petals 
closed or almost closed distally (Figure 2A). 
Decrease in relative width during ontogeny. Paired 
petals of equal length (17-26%TL), but slightly 
shorter than anterior petal in ambulacrum III (23- 
32%TL); extend about two-thirds of the way to the 
ambitus; maximum width varying between 10- 
17%TL; relatively broad in juveniles (Figure 2E), 
narrowing slightly during ontogeny; petals widest 
at about mid-petal length. Interporiferous region 
6-ll%TL, being widest in smallest specimens 
(Figure 2E). Inner pores of each pair circular; outer 
pore elongate; connected by shallow 
interporiferous furrow. 
Adoral surface concave, sloping at low angle to 
sunken peristome. Peristome circular, large, 
diameter 8-13%TL; central or slightly anterior of 
centre; bourrelets absent. Food grooves very short 
and weakly developed, extending less than a 
quarter of the distance from the persitome to the 
ambitus in the largest specimens (Figure 2F). 
Periproct circular to transversely oval; 4-7%TL in 
width; smaller than peristome and usually situated 
less than twice its length from the posterior border. 
However, in two very large specimens (WAM 
82.2095 and 85.2025, TL 43.2 mm and 44.7 mm, 
respectively) periproct situated greater than twice 
the periproct diameter from posterior ambitus. 
Discussion 
The Late Pliocene Peronella ova can be 
distinguished from the Late Pleistocene to Recent 
P. orbicularis by its relatively narrower, lower test 
with thicker margins; longer petals; larger 
peristome; weaker, shorter food grooves; and 
periproct situated closer to the posterior ambitus 
(except in very large specimens). It differs from 
another living Western Australian species, P. 
tuberculata Mortensen, 1918, from northwestern 
Australia, in possessing a relatively narrower test; 
periproct situated closer to the posterior margin; 
shorter food grooves; and flatter adoral surface. P. 
ova differs from the Middle Pleistocene P. ricta in 
possessing a lower test with thicker margins; 
relatively broader, longer petals; more concave 
adoral surface with slightly larger peristome and 
weaker, shorter food grooves. 
The other Australian Pliocene species of Peronella 
is P. platymodes (Tate, 1893) from the Late Pliocene 
Hallett Cove Sandstone. This species has a much 
thinner, narrower test than P. ova, combined with 
appreciably shorter petals. Of the four Pliocene 
species of Peronella described from Okinawa by 
Cooke (1954), P. ova most closely resembles P. 
kamimura Cooke, 1954. However, the Australian 
species can be distinguished by its longer petals 
that are closed distally and periproct situated 
closer to the posterior margin. 
Peronella ricta (Gregory, 1892) 
Figures 3, 4 
Laganum decagonale rictum Gregory 1892: 435-437, 
P1.12, figures la-c; Mortensen 1948: 271. 
Peronella ricta: Clark 1946: 34. 
Peronella lesueri (sic.): Logan et al. 1970: 56, 62, 73, 
figures 10-5,16-7. 
Peronella rictum: McNamara 1988: 158, figure 12.5. 
Material Examined 
Holotype 
BMNH E3770 (Gregory 1892, figures la-c) from 
the "Cainozoic. Shark's Bay, West Australia". 
Other material 
WAM 1808; 11027; 66.805; 78.352-78.354; 81.610 
(3); 83.771-83.782, 83.799 - 83.815; 87.545 (66 
specimens); 89.409 (five specimens); 96.208; 96.209 
from the Gladstone Member of the Carbla Oolite 
(Middle Pleistocene), approximately 2 km south of 
Gladstone Jetty to about 100 m north of the Jetty, 
from outcrops of limestone that occur in the inter¬ 
tidal zone, 200 - 300 m seaward of high water mark. 
Diagnosis 
Moderately large species of Peronella with 
relatively narrow, thick test; relatively narrow 
petals that are distally closed and extend just over 
half way to ambitus. Adoral surface of test almost 
flat. Food grooves short but moderately sunken 
proximally. Periproct less than twice its diameter 
from posterior margin. 
