NOTES ON THE OPHIURANS, OH THE SAND AND BRITTLE STARS. 345 
or crushing is hypothetical. The tooth papilla? (fig. 4, t.p.), 
which in some genera form a symmetrical group close to the 
lower margin of the jaw plate, merge gradually into five teeth 
above. They cannot act as crushers, and indeed in many species 
those of the five angles are widely separated below, so as to form 
a funnel-shaped opening to the mouth, leading to the narrow 
space above, where there may be only two or three teeth on each 
plate (fig. 4). Lately Danielssen and Koren and myself have de- 
scribed species in which the true teeth are divided, pointed, and 
irregular, and yet the Ophiurans were invariably large and well 
nourished. There is no rule about the closeness or open con- 
dition of the mouth canal between the jaw angles after death. 
In some specimens the teeth are in apposition, and the mouth 
papillae (fig. 9 m., p.) 9 nearly close the sides of the angles ; but 
in others it gapes and rigor mortis fixes it slightly open. 
Moreover, small Lamelibranchs, as I have lately had an oppor- 
tunity of finding, get into the stomach, but their delicate valves are 
not crushed; and Foraminifera are to be found there, compara- 
tively uninjured, besides much mud. The masticating and chew- 
ing does not take place. The mouth papillse, situated on the sides 
of the jaw angles (fig. 9, m.p.), are evidently filterers, and so are 
the tooth papillse. The true teeth keep out trespassers from 
the stomach, but none of them are used to crunch or smash 
nourishment, and the wonder is how the creatures manage to 
poke good-sized pieces of oysters into their mouths. The ten- 
tacles within the angles are of immense importance in this pro- 
ceeding, and it is very conceivable that the usual and normal 
food is finely triturated mud, containing minute organic bodies. 
It is clear that in some species the moving outwards of the jaw 
angles from the axis must be of the slightest description ; for the 
mouth apparatus is rendered unyielding in them, by the side 
mouth shields being united under the arm in a continuous 
zone. On the other hand, some extra limit may be granted 
by the non-union and generally rudimentary condition of the 
side mouth shields in some genera. Possibly some movement 
of the jaws towards each other centrally, may occur, first above 
and then below, and it is conceivable that movements of the 
arms from side to side, and from above downward, rare as 
these are in some kinds, must contribute to slight movements in 
the jaws. Some kinds, however, keep their teeth closed in spite 
of great wriggling. In fact, the more the matter is examined 
into, the more difficult it is to understand, not only how the 
Ophiuran bites and chews, but how it bolts a morsel; and 
certainly it does this last performance, whatever doubt there 
may be about the first. The stomach has some fibres, both 
longitudinal and circular, and some are close to the line 
where it is attached in festoons, above and external to the 
