RECORDS OF V/.A. MUSEUM. 
[163 
actinostome is 32 mm. across and the abactinal system is 24 mm. 
When other adult specimens (i.e., over 60 mm. L.d.) are taken into 
account, we find that these differences sum up to about this; in the 
eastern species the abactinal system is .50-. 60 of the actinostome, 
while in the western form it is .65-. 75. The most obvious character 
of the new species, however, is seen in its slender spines ; the largest 
primaries are from 1.3 to 1.6 mm. in diameter where thickest (near 
base) and as they are 75-80 mm. long, they appear very slender as 
compared with rodgersU ; in rcdgenii the primaries are 2-3 mm. in 
diameter, at least near base, and seldom exceed 75 mm. in length. 
This difference in the primary spines gives the two species totally 
different facies. There is also a noticeable difference in colour, in 
the specimens I have seen, though it may not prove a constant one; 
in rodgeysii, the colour is more or less purple, sometimes almost 
black, again deep crimson rarely brownish-red; in tenuispinus, the 
colour is reddish-brown or dull greenish, with no trace of purple. 
The pedicel lariae in the two species do not seem to differ ex- 
cept in relative frequency. Thus in specimens of rodgeysii, slender 
tridendaie pedicellariae seem to be very rare. Mortensen did not 
find them, and I have only found one on six specimens from New 
South Wales. But in tenispinns they are very common all over 
the test and the valves may exceed 3 mm. in length. On the other 
hand, the stout tridentate pedicellariae with curved valves seem to 
be rather uncommon in tenuispinus. 
Between Fremantle and Geraldton, W.A. Two specimens. 
No. 4,936. The light-coloured one is the Type. 
It is of course possible that larger series of specimens than are 
available to me, will show that this supposedly new species is only 
a form of rodgersii, but the general appearance is so different, I have 
little hesitation in giving it a new name. And I am confirmed in 
this by finding that the specimens of C. rodgersii recorded by A. 
Agassiz (Rev. Ech. pt. i, p. 98) from “ Houl man’s Abrolhos” are 
the slender spined western form and not typical rodgersii-, at any 
rate this is true of the specimen in the M.C.Z. collection. This 
specimen is young (only 47 mm. h.d.) but when conrpared with a 
specimen from Port Jackson, 43 mm. h.d-, its smaller actinostome 
and its much more slender primary spines are noticeable. 
