I 
Plio-Pleistocene Perotiella 
Species of Perottella are of limited 
biostratigraphical value in the western part of the 
continent (Figure 6). The Middle Pleistocene P. ricta 
has only been recognised with certainty from a 
very restricted area of Shark Bay. Four poorly 
preserved specimens of Peronella from the Middle 
Pleistocene of the Perth Basin near Busselton, 
appear much closer to P. orbicularis than they do to 
P. ricta. In the Carnarvon Basin P. orbicularis is 
restricted to the Late Pleistocene and Holocene. As 
Figure 7 Peronella lesueuri (Valenciennes, 1841) from 
the Middle Holocene Herschel Limestone, 
Lake Baghdad, Rottnest Island, Western 
Australia: A, B, WAM 77.516; xl. 
201 
such, species of Peronella have some 
biostratigraphical utility in the Carnarvon Basin, 
allowing Middle and Late Pleistocene emits to be 
characterised. The well-known living P. lesueuri 
appears to be restricted to the Holocene in the 
Perth and Carnarvon Basins. This species is 
morphologically quite distinct from the other 
species described herein, attaining a much larger 
size, having a much thinner, flatter test and petals 
that distally are open (Figure 7). It is a common 
element in Holocene deposits in the Swan Estuary 
(Yassini and Kendrick 1988) and occurs in the 
Herschel Limestone, a unit of the same age, on 
Rottnest Island. > 
While Pliocene sediments occur extensively 
subsurface in the Perth Basin (Kendrick et al. 1991) 
only rare, indeterminate fragments of Peronella are 
known, unlike coeval sediments in the Eucla Basin 
where P. ova is common. The dominant 
clypeasteroid that occurs within the subsurface 
Pliocene Ascot Formation in the Perth Basin is 
Ammotrophus, a genus restricted to southwestern 
Australia today. This form, however, is not present 
in the Roe Calcarenite in the Eucla Basin. 
ACKNOWLEDGEMENTS 
I am grateful to George Kendrick for helpful 
discussions, mollusc identifications and assistance 
in the field, and to Sue Radford, Jamie, Katie and 
Tim McNamara for help with collecting specimens 
in the field. Thanks to Kris Brimmell for the 
photography, Danielle Hendricks for drafting and 
Steve Donovan and Burt Carter for helpful 
comments on the manuscript. 
REFERENCES 
Agassiz, A. (1872). Revision of the Echini. Memoirs of the 
Museum of Comparative Zoology, Harvard University 3: 
1-762. 
Agassiz, L. (1841). Monographies d'Echinodermes Vivans et 
Fossiles. II. Les Scutelles. Jaquet, Neuchatel. 
Clark, H.L. (1946). The echinoderm fauna of Australia. 
Its composition and its origin. Publications of the 
Carnegie Institution 566: 1-567. 
Cooke, C.W. (1942). Cenozoic irregular echinoids of 
eastern United States. Journal of Paleontology 16: 1-62. 
Cooke, C.W. (1954). Pliocene echinoids from Okinawa. 
United States Geological Survey Professional Paper 264- 
C: 45-53. 
Davies, G.R. (1970). Algal-laminated sediments. 
Gladstone Embayment, Shark Bay, Western 
Australia. Memoirs of the American Association of 
Petroleum Geologists 13: 169-205. 
Durham, J.W. (1954). A new family of clypeasteroid 
echinoids. Journal of Paleontology 28: 677-684. 
Foster, R.J. and Philip, G.M. (1980). Some Australian 
Late Cainozoic echinoids. Proceedings of the Royal 
Society of Victoria 91:155-160. 
