Recent and Fossil Hy dractiniide. 301 
chitinous species just described. On the smooth species of 
Nerita, to which I have alluded, the development of the 
branch can be followed throughout from the spine of the 
polypary to its ultimate form, which in the largest specimens 
is about 1-10th inch in diameter and 1-4th of an inch long, 
with a tendency to assume a compressed, palmate, bifurcate 
shape at the free extremity. So it should be remembered 
that the calcareous polypary of Hydractinia calcarea may 
also be branched like the chitinous one of H. arborescens. 
Hydractinia Kingti, n. sp. 
Fossil. Polypary massive, growing over a turreted shell, 
somewhat like that supporting Hydractinia arborescens, com-- 
pressed, extending here and there irregularly into a short, 
thick lobe, process, or branch. Composed of compact, greyish- 
white limestone. Surface uniformly even, thickly veined with 
anastomosing grooves amongst granular ridges once surround- 
ing the holes of the polypites, which are now tilled up and undis- 
tinguishable from the rest of the calcareous material; pustu- 
liferous—that is, presenting numerous depressed papillary 
elevations, which are the representatives of the spines in other 
species, and where broken open (as many are) disclosing the 
grooved venation on the surface of the subjacent layer. In- 
ternal structure concentrically laminated, presenting in a 
vertical section rows of chambers (?the hollow bases of the 
pustules of each layer), between which are the vertical tubes 
of the polypites, now, for the most part, filled with calcareous 
matter, but, where still hollow, possessing a diameter of 
3-1800ths inch, and at their openings into the roofs of the 
chambers respectively a calcareous diaphragm with central 
hole, similar in form to that of Hydractinia calcarea (§ Annals,’ 
1877, vol. xix. p. 51, pl. viii. fig. 4, g g), but apparently 
without its repetition which is seen along the vertical tubes in 
Hydractinia pliocena—a point, however, that must be de- 
cided by a more favourable specimen than the one which I 
possess. Size of the fragment from which the above descrip- 
tion is taken about an inch square and half an inch thick. 
Thickest portion of the polypary from the shell outwards 
§-12ths inch ; largest lobo-branch, which is circular in the 
section, but whose extremity has been broken off, 4 inch in 
diameter, and the same in length. 
Hab. Marine, on a turreted shell like Phos senticosus ; or it 
may have been a Cerithium, as there is only a fragment of 
the apex left in the specimen for this determination. 
Loc. ? Subapennine strata. 
Obs. At first I thought this was a specimen of Hydractinia 
