Mr. E. A. Smith on two new Species of Shells. 441 
a transverse row of five spines. The adambulacral plates are 
convex towards the ambulacrum, and carry on their inner 
edge three or four spines ; the other spines on these plates are 
stouter, with blunted ends, and would seem in younger ex- 
amples to have been arranged in two or three regular longi- 
tudinal rows; such regularity, however, is considerably ob- 
secured in well-grown specimens. ‘The rich supply of stout 
blunt spines which distinguishes the adambulacral region and 
the infero-marginal plates is a characteristic also of the inter- 
mediate plates on the ventral surface, the transverse axes of 
which are completely covered by them, about ten being, in the 
larger specimen, found to be set in one more or less regular 
line at the angle of the disk. 
The madreporic plate is large, and, though not projecting, 
is very distinct; it is distant a little more than its own 
diameter from the edge of the disk. The abactinal surface 
of the larger specimen is greyish brown, and of the smaller 
orange-yellow ; both are, unfortunately, dried. 
Like Archaster angulatus, A. magnificus attains a con- 
siderable size, but, as compared with that species, has the 
skeletal plates of its arm distinctly not so stout; it is possibly 
in consequence of this that we find the spines themselves so 
richly and so well developed. 
Indeed we have much evidence in support of the generali- 
zation that in littoral species, at any rate, the strength and 
number of the spines is in inverse proportion to the stoutness 
of the skeletal plates: when these are strong, the starfish is 
enabled to withstand the bite of an enemy ; but when they are 
weaker, a defensive apparatus is provided in longer, stronger, 
and stouter spines. 
XLVI.—Description of two new Species of Shells. 
By Ene@ar A. Smita. 
Cyprea fallax. 
Testa pyriformi-ovata, postice subumbilicata vel excavata, lutea, 
maculis albis parvis notata, basi marginibusque albis; labrum 
mediocriter crassum, postice aliquanto productum, dentibus 23 
subsequalibus munitum; labium internum dentibus 23 paulo 
minoribus parum prominentibus instructum. Longit. 36 mill., 
lat. 20. 
Hab. West Australia. 
This shell closely resembles the common: C. cribraria; but 
I venture to describe it as a new species for the following 
Ann. & Mag. N. Hist. Ser. 5. Vol. viii. 31 
