106 DEVONIAN FOSSILS 
(2) The difference in ornamentation on the different parts of 
the mature shell means that the young forms have quite a 
different appearance from the older ones. 
(3) Specimens 27,231 and 27,216 show corals growing on Hip- 
parionyx shells. 
(4) Hipparionyx major is the biggest Lower Devonian brachio- 
pod known in Australasia, and perhaps in the world. 
(5) The costellae of the outer surface show clearly on the margin 
of the inner surface of the shell. Inside that margin is the 
papillate area. There are no papillae on the costellate margin 
of the inner surface. So apparently the shell was thickened 
by secondary deposition on the inside of the shell, and the 
papillae were part of the secondary growth. 
Points of evolutionary and palaeogeographic interest are: 
(1) Hipparionyx minor and Н. proximus form an evolutionary 
sequence in the Lower Devonian rocks of North America, the 
former being characteristic of the Chapman sandstone and 
the latter of the succeeding Oriskany sandstone. H. proximus 
is essentially a more developed H. minor. Such a sequence 
appears to be present in the Lower Devonian rocks of 
Victoria. Brachiopods from the Lilydale district have been 
referred to H. minor (Gill, 1942), and H. major sp. nov. is 
essentially a more developed H. minor, hence the trivial name. 
Although H. major is distinct from H. proximus, it is never- 
theless comparable with it in degree of development and in 
size. In view of this evolutionary trend, it is likely that the 
beds containing H. major are a little younger than those 
containing H. minor. A similar conclusion is reached from 
the study of Chonetes baragwanathi sp. nov. and Protolepto- 
strophia affinalata sp. nov. 
(2) The massive character of the cardinalia, and the development 
of adventitious growth lines and rugae, may be interpreted 
as evidences of phylogerontism. Such evidences are present 
also in Chonetes baragwanathi. Hipparionyx is an offshore 
facies shell, but ponderous forms like H. major are not char- 
acteristic of that environment. 
(3) Hippariony« is widespread in Victoria, occurring in many 
localities in the Lilydale area, at Mooroolbark (Hull Road), 
