Page:Scientific results HMS Challenger vol 18 part 2.djvu/94

970

Definition.— with four large lateral gates, without basal gate. Skeleton composed of two complete vertical rings, perpendicular one to another—the primary sagittal and the secondary frontal ring.

Definition.— with four large, simple, lateral gates, without basal gate and lattice-work. Skeleton composed of two simple meridional rings, perpendicular to one another.

The genus Zygostephanus, founded by me in 1862 for the Mediterranean Zygostephanus mülleri, is the simplest and most primitive of all the Coronida, and may