MUSEUM OF COMPARATIVE ZOOLOGY. 27 



small, prominent, rounded, soft venucse, having the outer surface composed of 

 a layer of special nettling cells; these verrucas also extend over the basal part 

 of the lower calicles. They may, perhaps, be of the same nature as the zooids 

 of Pennatulacea. 



Iridogorgia Pourtalesii Verrill, sp. nov. 



Plate II. Figs. 7, 7 a. 



Main stem strong, rather rigid, calcareous, growing in a remarkably regular, 

 open, upright spiral or helix. Base not obtained. Branches numerous, long, 

 slender, delicately tapered, flexible, undivided; they arise very regularly, at 

 intervals of about 4 to 6 mm., in a single row, along the side of the main 

 stem that forms the outside of the spiral, and spread out laterally and widely, 

 nearly at right angles to the stem, so that the whole coral has a broad spiral 

 form, something like the skeleton of a spiral staircase. 



The axis, in our example, makes about five volutions; its apex becomes 

 slender and acute, but the lower end is incomplete. 



The ccenenchyma is thin, and filled with slender fusiform spicula beneath the 

 surface, which is soft, and bears numerous minute, rounded, elevated, soft ver- 

 ruca;, which cover the main stem and proximal part of the branches, extending 

 also over the basskl portion of their proximal calicles, but they gradually be- 

 come smaller and disappear farther out on the branches. 



Calicles are not found on the main stem, except rarely one close to the origin 

 of a branch; on the branches they are placed singly, and rather far apart, along 

 the upper side; the distance between them is usually from 5 to 10 mm. The 

 calicles are mostly broader than the branches on which they are situated; they 

 have a swollen basal part, extending somewhat along the branch; the upper 

 part is verruciform, and is usually surmounted by the large, incurved tentacles, 

 which do not appear to be capable of entire retraction. The proximal calicles 

 (Fig. 7) are the largest, and have very large tentacles, with swollen translu- 

 cent stems, in which there are only a few slender spigula, close to the base; the 

 pinnae are elongated, slender, and without spicula. The calicles are filled with 

 slender, nearly smooth, acute spicula, oblique and transverse in the basal por- 

 tion, but becoming longitudial at the summit, between the bases of the tentacles. 



In alcohol, the color of the calicles, tentacles, and ccenenchyma is white; the 

 denuded axis and branches have a bright golden or pale bronze-like lustre, 

 and reflect brilliant iridescent colors, in which light green and golden yellow 

 predominate; by transmitted light the axis of the branches is pale wax-yellow 

 and light amber. 



Height of main stem, 200 mm. ; diameter at lower end, about 2 mm.; diam- 

 eter of larger branches, at base, 1 mm. or less. The larger, upright, fusiform 

 spicula in the distal part of the calicles measure .56 by 04, .48 by .04, 

 .46 by .05, .42 by .04 nmi.; those of the basal part of the calicles, .55 by .05, 

 .55 by .04, .52 by .05, .50 by .04, .42 by .035, .42 by .025, .28 by .03, 



