The Atoll of Funafuti, Ellice group : its zoology, botany, ethnology and general structure based on collections made by Charles Hedley of the Australian Museum, Sydney, N.S.W.
Culcita acutispina, Jef. Bell
Culcita acutispina, Jef. Bell.
Culcita acutispina, Jef. Bell, Ann. & Mag. Nat. Hist. (5), xii. p. 334.
To this species are referred, though with some hesitation, two specimens obtained in the lagoon. Generally both examples agree with the description given by the author, there are, however, a few characters present which are only slightly touched upon in the original diagnosis.
In the larger specimen the adambulacral spines are in two rows, the inner consisting of four or five spines to each plate; they are a little compressed, the central three being the longest. The outer row consists of two spines to each plate which are very unequal in size, the one nearest the actinostome is large, bluntly conical, and not as a rule higher than broad at the base. The smaller outer spine is almost undistinguishable from the granules which beset the surface generally; occasionally, however, they are more evident, and resemble the larger spines of the inner row.page 158
The central interambulacral space of the actinal surface is closely studded with bead-like granules, varying in size from one to two millimetres in diameter. They are not seriate but scattered irregularly, and are either in contact with each other at the base or separated by a few granules.
On the space near the mouth angle, along the ambulacral groove and on the sides below the porous areas, the large granules are mostly acute, about as high as broad, and are at least their own diameter apart.
The sides of the porous areas and the whole of the abactinal surface is furnished with spines, narrower at the base and more acute than any of those on the actinal surface. The larger spines are mostly confined to the interporous spaces, and—in the large specimen under notice—give the upper surface a reticulate appearance.
In the smaller example the large acute spines are scattered over the porous and non-porous areas alike, and the areolate feature visible in the larger specimen is wanting. These spines are usually a little higher than broad, and two or three times their diameter apart.
The porous areas are densely packed with short acute spines, subspiniform granules and pedicellariæ;, the latter are about two-thirds of a millimetre in length; when viewed from the lateral aspect they are seen to be slightly convex externally and meeting-only at their tips.
Each pedicel is narrow in the middle with the base and apex dilated, the latter has its inner surface excavated, and the semi-circular margin minutely denticulated. The pedicellariæ; are much more abundant on the lower half of the abactinal surface than in the upper central region,—usually from six to ten in a centimetre,—they are mostly confined to the porous areas, but occasionally they occur on the interporous spaces.
The minute granules on the abactinal surface are more or less acute and a little longer than broad at the base. The somewhat larger granules on the actinal surface are also mostly acute and about as high as broad; very few are rounded at the summit.
The pedicellarise on the actinal surface are not very abundant, the majority are elevated a little above the adjacent granules, and present when closed an almost circular outline, some of the larger, however, are a little elongated.
Owing to their slight elevation, larger size, and lighter colour, the actinal pedicellariæ; are quite conspicuous and easily distinguished from the small granules.
The madreporic plate is oval in shape, and has a few conical spines around its margin, similar spines surround the anus, and in the larger specimen some of the spines are granulose at the apex.page 159
The number of marginal pore areas in the interambulacral space is thirteen in both specimens. Prom the margin to the anus there are nine or ten pore areas, and from the tip of the ambulacral groove to the anus there are seven in the large specimen. In the smaller example they are fewer, being eight or nine in the interambulacral space, and five from the apex of the arm to the anus.
There are seventy clusters of adambulacral spines along each side of the ambulacral groove, counting from the mouth angle to the end of the groove.
The following are the measurements of both examples:—
|Large specimen||R., 155mm.; r., 100mm.|
|Small ditto.||R., 115mm.; r., 85mm.|
R., measured along the side of the groove from mouth angle to the extremity of the arm; r., from mouth to commencement of pore areas.
|Diameter, large specimen||220mm.|
|Height large specimen||85mm.|
|Diameter, small specimen||172mm.|
|Height small specimen||60mm.|
An examination of the members of the genus Culcita shows that it is greatly in need of revision; too much attention has been paid to the outward form, which presents characters of little specific value.
If a specimen is obtained and placed in a vessel with sea water, and allowed to assume a symmetrical shape, and afterwards killed in strong spirit, when thoroughly preserved it may be dried and will retain its shape, having the abactinal surface convex. If on the other hand it is plunged direct into strong alcohol without regard to its shape, it will retain its original and often very unsymmetrical form. Cake-like or fiat examples are in most cases due either to drying without previous curing in spirits, or drying after being in very weak spirit.
In Anthenea acuta, Perrier—common in Port Jackson—we have a good example in illustration of the above remarks.
This species often attains to nine or ten inches in diameter, and is a most variable species as far as the convexity of the abactinal surface is concerned and in the granulation. Having trawled thousands of specimens, and noted that, however unsymmetrical when brought up in the trawl, if placed on a level surface in a little sea water they soon regain their natural form, and may be killed in that state either by flooding them with fresh water or by placing them in strong spirit.page 160
It has often happened when we have obtained the Anthenea in abundance that some have been lying about the deck, others entangled in the trawl, or buried beneath the seaweeds for many hours. Ultimately these specimens have been hastily gathered up and placed in spirits, resulting in a series of distorted examples, which would be very misleading to a worker un-acquainted with the form of a well preserved specimen.
The following are the measurements of four specimens of Anthenea acuta, Perr., showing the differences due to the mode of preservation:—