Mr. E. A. Smith on a new Species of Spatangide. 69 
decidedly smaller and much more numerous, whilst the geni- 
tal pores are larger. On the lower surface there are differ- 
ences also: the plastron is conspicuously narrower and the 
oral aperture is considerably broader transversely. 
The course of the peripetalous and lateral fascioles in Z. 
australis is subject both to variation in different specimens 
and also to irregularity in the same individual. In normal 
specimens the first forms but a single angle some distance 
within in each interambulacral space; but in others, as is the 
case in the variety figured by Gray (Cat. Recent Echinida, 
1855, pl. vi. fig. 2 a), it becomes biangular at its highest part 
both in the anterior and lateral interambulacra. 

Linthia rostrata. 
a, actinal view ; 0, abactinal ; c, lateral; d, anterior. 
The lateral fasciole in the same specimen is also irregular. 
On one side its position is normal; but on the other, from the 
point of contact with the peripetalous fasciole, it rises obliquely 
for the distance of nearly three quarters of an inch within the 
posterior lateral interambulacrum, then forming a sudden bend 
descends at right angles for half an inch, and, again bending 
less acutely, pursues the ordinary course, passing under the 
