The stomodum is formed as an epiblastic pit between the two procephalic lobes (figs. 200 and 205, st).
procephalic lobes: in the embryo, form part of the anterior, overhanging portion of the head.
In the procephalic lobes the epiblast is much thickened, and is formed of several rows of cells.
The caudal and procephalic lobes are very similar in appearance, but the procephalic lobe is slightly the wider of the two.
An upper lip or labrum is formed as an unpaired organ in the line between the procephalic lobes.
The six segments behind the procephalic lobes are the six largest, and each of them bears two prominent appendages.
The supra-œsophageal ganglia are formed independently of the ventral cords as two thickenings of the procephalic lobes (fig. 205).
There is a distinct ganglionic thickening for the chelicer quite independent of the procephalic lobes.
The most anterior line marks off a pr-oral segment, which soon sends out two lateral wings—the procephalic lobes.
Epicranial suture: the line of junction of the two procephalic lobes.
procephalic pro·ce·phal·ic (prō'sə-fāl'ĭk)
Relating to or located on or near the front of the head.
cephalic ce·phal·ic (sə-fāl'ĭk)
Of or relating to the head.
Located on, in, or near the head.