from the Miocene of Australia. 103 
With these large plates stereotyped and immovable, a bar to 
downward movement on the part of the later formed plates is developed 
at or near the ambitus. It appears that in ZLovenra there is no 
interruption in the production of new coronal plates from the oculars 
(at least during a large portion of the growth: period of the individual), 
so that the lower (older) members of each column become jammed 
against the adapical margins of the large plates. This assumption 
TEXT-FIG. 2.—Specimen B of Lovenia forbes: for comparison with Fig. 1. It 
will be noticed that the two figures are identical exceptin proportions and 
the degree of reduetion of the interambulacral plates at the ambitus. 
receives strong support from the fact that in this species the greatest 
degree of compression of the plates occurs in the neighbourhood of 
areas IJ and IV. ‘The actual distance (measured on the curve) 
between the ocular plates and the adapical margins of the large 
adoral plates is less along those two areas than in any other part of 
the test, while the number of plates in each interambulacral column 
is the same over the whole test. Conversely, the distance from 
