K antero-postero median section 6, 7, with following additions.
F, Postero-dorsal surface.
6, Postero-internal pillar or column.
Conifera; the star represents the ciliated cup connected by ciliated depressions with the groove; 5, disk of Conochilus, like the Bdelloid, but with mouth antero-dorsal, the gap postero-ventral; 6, disk of Stephanoceroscingulum broken up into setiferous lobes, groove a naked funnel, trochus a horseshoe-shaped ridge, mouth central.
The trochus forms the powerful currents for locomotion, and for the supply of food material, while the cingulum produces a local current round the upper rim of the corona to bring the food particles direct to the mouth, which is displaced through a postero-ventral gap in the trochus to lie behind the disk, just as occurs in the more specialized Ciliata.
2, 5), a Melicertan, the mouth is displaced towards the antero-dorsal side and the gap is postero-ventral.
Where the whole crop is strengthened by a framework of bars, the incudate mastax lies in a little postero-ventral pouch which can be everted through the crop and mouth.
- There is a large ganglion lying in close contact with the pharynx, proximal to the crop and on its antero-dorsal side; in Bdelloidaceae at least it is united by short connectives with a smaller postero-ventral ganglion to form a nerve collar.
The eyes are refractive globules set in a cup of red pigment traversed by a nerve fibre, and lie on the proximal side of the body, directly on the postero-dorsal surface of the brain, or at a little distance from it, on the neck, often within the circle on the corona, and usually well within the transparent body.
Typically there are two pairs - a proximal, more or less approximated on the postero-dorsal surface, and a distal pair, more widely separate.
- a, Microcodon clavus, showing corona, lateral antennae and jointed foot; b, Rhinops vitrea, corona from below, showing proboscidiform extension containing eyes; c, Philodina megalotrocha; d, head of Rotifer macroceros, postero-ventral view, showing lobes of corona, and antero-dorsal median antenna, telescopic with setae; e, Rotifer (Actinurus) neptunius, showing head with retracted corona, and protruded dorsal proboscis bearing median antenna, and telescopic foot with toes and spurs; f.
(b) Triarthridae; body with a pair of long cervical spines pointing distally and serving for leaping movements or to extend the body and make it too big for small enemies to swallow; Pedetes Gosse (no median spines); Triarthra Ehr., one postero-ventral spine; Tetramastix Zacharias, two unequal median spines.
In the majority of Trilobites this groove passes backwards from the anterior or anterolateral edge of this plate to its posterior or postero-lateral border, dividing it into an inner portion continuous with the flabellum and fused tergal regions, and an outer portion bearing the eye.
The cheek-teeth, which have crowns of moderate height, differ from those of all the foregoing in that the postero-internal pillar (the projection on the right-hand top corner of c in fig.