(I) The polyp, when present, is without the strongly developed longitudinal retractor muscles, forming ridges (taeniolae) projecting into the digestive cavity, seen in the scyphistoma or scyphopolyp. (2) The medusa, when' present, has a velum and is hence said to be craspedote; the nervous system forms two continuous rings running above and below the velum; the margin of the umbrella is not lobed (except in Narcomedusae) but entire; there are characteristic differences in the sense-organs (see below, and Scyphomedusae); and gastral filaments (phacellae), subgenital pits, &c., are absent.
Interradial septal ridges, passing into the taeniolae (f.t) in the stalk.
In forms such as Lucernaria and Charybdaea, in which the umbrella is of deep form and the stomachcavity consequently of great extent in the vertical direction, the concrescence-areas or septal nodes are drawn out into vertical partitions or taeniolae (fig.
4, L.o.c.), resembling in their anatomical relations the mesenteries of the Anthopolyp. The phacellae are carried on the edges of the taeniolae (fig.
Endodermal muscles are found in the phacellae, and in such forms as Lucernaria, longitudinal (vertical) muscular tracts or bands are found in the taeniolae, which, according to some authorities, are xxiv.
The internal gastric cavity of the scyphistoma is not a simple space as in the hydropolyp, but is subdivided by four ridges or taeniolae, arising one in each interradius (fig.
The septal ostia become widened and the gastral cavity flattened, whereby the taeniolae become comparatively shallow columns, similar to the septal nodes or cathammata of other forms.'
By their contraction the muscles of the taeniolae drag the hypostome down and so produce the appearances which have been interpreted as a stomodaeal invagination.