384 Zoological Position of the 1 Bulldog ’ Ophiurans. 
phological differences between the two sets of specimens 
might have arisen from the differences in their struggle for 
existence. The deep-sea form is suggestive of plenty of food 
got with little trouble, and of want of exercise in the profound 
depths; it is coarser than the others; and its tentacular 
apparatus and tentacle-protectors are the least developed. 
The spines of the side arm-plates are smaller in relation to 
the arms in the deep-sea form than in the others; and the 
mouth-papillcB are coarser, larger, and wider apart in the first- 
mentioned kind. 
The spinulation of the upper part of the dish is very close 
and tolerably equal in all the specimens, whether from deep 
or shallow water; but there is much variety in the shape of 
the spines. In the shallower-water forms the typical short 
round-topped cylinders, with a crown or head of numerous 
and minute thorns, are seen in some specimens ; but in others, 
and in the specimen from the great depth, the spines are 
longer, slender, tapering, and terminate in from one to four or 
five very sharp unequal thorns. Underneath the disk, in the 
interbrachial spaces there is the same ornamentation. More¬ 
over, whilst in some specimens the spine is situated on a very 
distinct scale of its own, marked with concentric rows of dot¬ 
like appearance, and which consist of very minute spinules, 
in others, and in the deep-sea form, I have failed to notice 
this very elegant ornamentation. 
The lower arm-plates bulge somewhat in the deep-sea form, 
and the side arm-plates have as great a development as is 
possible in a member of the genus. 
In perfect specimens of the species there is a large rounded 
tentacle-scale just above the outer mouth-papilla, and the 
tentacle comes out between it and the papilla. This is not so 
well seen in the form under consideration. Under the arm, 
on the edge of the first side arm-plate which does not come 
quite to the median line, is a large tentacle-scale, broad and pro¬ 
jecting directly downwards. The other tentacle-scales are large 
and rounded. This is the case in typical specimens ; but in 
the deep-sea form the projecting scales are less evident, and 
the others are small, often narrow, and even like a small 
spine. Far out on the arm, where the side arm-plates form 
the greater part of the under surface, the scale is still seen, 
but it is like a minute spine in shape. 
The main morphological details, howmver, of the specimens 
obtained by Dr. Wallich are the same as those decided to be 
characteristic of the species Ophiacantha spinulosa by Muller 
and Troschel. 
