96 A. E. Verrill on Echinoderms and Corals 
is due 0 age, though some specimens are more elevated toward 
the apex than others; in regard to the flatness or concavity of : 
the lower side there is, however, great variation, though > 
Gray used this character in dividing the genus into sections 4 
The youngest specimens are 2°30 long by 2°10 wide, and are 
more oval in form and scarcely angular, but have the flatness 
and form of ambulacral rosette characteristic of the ge spect 
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ce ome of the th ee cd by Dr. Gray from the Indo-Pa- 
cific faunse (C. Australasia, C. testudinarius) seem to be more 
settle the true relations of these species. It may be that 
inarius is the same and its localit organs its outline 
being nearly identical, but the upper side is said to be evenly 
convex, an Sas lower side concave ota the margin. 
Thi of especial interest as the first of the genus . 
known front ey Pacific coast of America, although the genus | 
was known to occur on nearly all other tropical coasts. 
tame nae Agassiz. 
there ae as be a sorte to close the anterior pair. The 
rior interambulacral opening is large and broad-oval with 
thickened borders in all, but there is a variation of more than 
50 per cent in its relative size; the region around it is in 
more elevated than the central region and cuadorstt swollen. 
The form of the ambulacral rosette varies considera The 
three anterior petals are subequal and usually long-oval, 
obtusely rounded at the end, but in one case they are narrower 
and more elliptical, especially the odd anterior one, which 1s 
widest in the middle, tapering to each end, and in another they 
are broader and more dilated outwardly than usual; the two 
posterior on ‘ and ¢ 
somewhat around the posterior o , but they vary consider 
: a3 in relative width. The followin ng are the proportions 
ee ae of sa Lens : 
