In the fenestrate division, in the whole of which the cells are of larger size and stronger than in the other, the wall of the cell appears to be constituted of at least two distinct laminae.  The external lamina, on the front of the cell, is perforated by a certain number of holes, is wanting rather in a certain number of spaces, for which spaces the term fenestrae is employed.  These apparent openings do not, therefore, penetrate into the cavity of the cell.  But besides the fenestrae, there is, in some cases, a small central opening which does penetrate through the wall.  In most cases the fenestrae are arranged in a crescentic, or rather horseshoe-shaped line, indicative, as it were, of the limits of a regular oval space, in the front wall of the cell, the upper part of which oval would be formed by the mouth, and the remainder filled up by the deposition of calcareous matter, as happens for instance in the older cells towards the bottom of the polyzoary in certain Cellulariae, etc.

A further characteristic of the fenestrate Catenicellae is the terminal position of the ovicells.  These organs are clearly transformed cells, or cells dilated to considerably more than their natural bulk, and assuming a subglobose form.  And what is worthy of remark, these terminal ovicells always have a sessile avicularium on the summit.

In the Vittatae the cell is smaller, and usually more delicate and transparent.  They probably want the outer lamina, or have it very thin, and consequently present no fenestrate spaces, and the front of the cell is beset (sometimes very sparingly) with more or less prominent, minute, acuminate papillae.  On each side, sometimes on the anterior aspect, sometimes quite laterally, is a narrow elongated band or vitta, as it is here designated, from which the distinctive sectional appellation is derived.  This band or stripe varies in width and proportionate length and position in different species; it is slightly elevated, and marked with larger, or small circular discoid, or acuminated eminences.  This subdivision is further distinguished by the situation of the ovicells, which are not terminal, but occur at irregular intervals on cells in the course of the series.  They are of the same galeate form as in many others of the Escharinae, but are not as in them placed above the mouth of the cell, but below it in front:  and in all cases the shape of the ovicell-bearing cell is much altered from the rest, and in all the vittate species the cell upon which the ovicell is produced arises from its predecessor, not with the intervention of a short tube, but is immediately sessile upon it, by a broad base.

a.  Fenestratae.

Cells large, fenestrate in front; ovicells terminal.

1.  C. hastata, n. sp. ?

C. bicuspis ?  Gray.  Dieffenbach’s New Zealand, Volume 2 page 293.

Fenestrae, 7 to 9, disposed in a crescent, and with elongated fissures radiating towards them from the median line.  Avicularia supporting a large pyramidal pointed hollow process, compressed, and perforated before and behind by five or six small circular pores.