Freyella heroina, n. sp. (Pl. CXIV. figs. 5-8).
Rays nine. R = 320 mm.; r = 10 mm. R = 32r. Breadth of a ray at the base, 5.5 mm.; at the widest part of the ovarial inflation, 8.5 mm.; and at 40 mm. beyond the disk, 4.5 mm.
Rays delicate and of remarkable length, cylindrical and narrow at the base, but almost immediately swelling rather abruptly into a short ovoid ovarial inflation of moderate tumidity, which hardly extends beyond 15 mm. from the base of the proximal twenty-first part of the ray. From thence the ray is subtriangular and tapers continuously to the extremity. The rays are distinctly spaced at the base, the interbrachial arcs being sharply rounded.
The disk is small, with the abactinal surface, which is subplane and capable of slight inflation, very little- higher than the base of the rays. The membrane covering the disk and the basal portion of the rays, to the limit of the ovarial region, is underlaid by a pavement of calcareous plates of suhhexagonal form, which appear rather widely spaced. The plating of the disk is invisible superficially, but that of the ovarial region may be clearly traced with a hand-magnifier. On the disk the plates bear only very small spinelets, about a millimetre in length or rather less, which taper slightly and are covered with simple membrane, and they are sufficiently numerous to give a fairly hirsute appearance to the disk. On the ovarial regions the spinelets are smaller and are congregated in little groups of three to five on the centre of each plate, and the groups have consequently a distinct and isolated appearance when seen with a low power. No pedicellariae occur normally among the spinelets on the disk and ovarial regions, but here and there a small sporadic one may be found. On the outer (distal) portion of the ovarial swelling, however, the spinelets diminish in number, and their place is taken by small crowded pedicellariae, which speedily fall into crowded transverse bands, the spinelets disappearing altogether. These pedicellariae are very small and measure from 0.12 to 0.15 mm. in length. Beyond the ovarial inflation the abactinal surface of the ray is covered with the usual delicate transparent membrane, bearing saddle-like sacccular [sic] bands crowded with minute pedicellariae, the corresponding bands on the two sides of the ray being united across the median keel.
The ambulacral furrow occupies nearly the whole of the actinal surface of the ray, measuring about 2 mm. in width at a part where the whole ray is 4 mm. The adambulacral plates are elongate, nearly 2 mm. in length, and form a narrow rounded margin to the furrow; their form is strikingly suggestive of a caudal vertebra; the adoral end of the plate is somewhat broader than the aboral, and the margin towards the furrow is rather deeply concave, the greatest depth lying between the median point of the furrow margin and its aboral extremity, where the plate stretches prominently into the furrow, forming a well-defined bay along which the ambulacral tube-foot passes, and by which it is separated from the succeeding tube-foot. The armature of the adambulacral plates consists of :—(1.) a small spinelet attached to the aboral prominence of the plate above-mentioned, and directed horizontally over the furrow and at a slight angle in the direction of the ray; (2.) a longer spine standing perpendicularly and articulated on a tubercular elevation on the middle of the actinal surface of the plate; and (3.) a lateral spine on alternate plates articulated on a tubercle-like rudimentary infero-marginal plate ankylosed on the lateral margin of the adambulacral plate. The small inner spinelet is rather more than a millimetre in length, and comparatively robust at the base; it is often flattened and expanded at the tip, which is truncate and subspatulate, the whole covered with membrane bearing a rather numerous congregation of pedicellariae. The perpendicular spine is delicate and tapering; the longest are about 5 mm. in length, but at 80 or 90 mm. from the disk they are not more than 2 to 3 mm., and their length generally appears to be rather irregular ; they are encased in a membranous sheath, with a more or less elongate saccular prolongation, and the whole is covered with crowded pedicellariae. On the ovarial region the distal extremity of these spines is usually expanded like the proximal articulatory base, and is truncate, which gives them a robust clavate appearance. The lateral spines are of great delicacy; the longest measure 16 to 18 mm., and they are encased in a sheath of very delicate membrane with crowded pedicellariae, and there is a comparatively large saccular knob at the extremity. The pedicellariae are exceedingly small and attached to the membrane by long thread-like stalks. Unfortunately, very few of these spinelets are to be found unbroken, owing to the extreme fragility and delicacy of the specimen, and probably also to the difficulty in detaching it from the hempen tangles. It is much shattered, and I am therefore unable to say with accuracy what the general habit of the ray would be in comparison with that of other species, but I am disposed to think that the lateral spines were relatively short in proportion to the great length of the rays, and that they were certainly more delicate than usual.
The actinostome is large and wide, its diameter being about 12 mm., in a disk measuring 19 mm. The buccal membrane is of great delicacy, and semitransparent. The mouth-plates are small and inconspicuous, and present a remarkably straight margin towards the actinostome. Two small mouth-spines are borne on each plate, of a peculiarly curved, semicrescentic or semiscimitar form; they have the appearance of bending round until the outward prolongation of the distal extremity is at a right angle to the prolongation of the median line of the mouth-plates, and their shortness gives them the appearance of being turned back so as to fit almost close to the margin of the plate. They are covered with thin membrane, and have a few pedicellariae near the base. Each plate bears on its actinal surface a secondary or superficial mouth-spine 4 mm. in length, .enclosed in a membranous sheath crowded with large pedicellariae. The entrance of the ambulacral furrow is barred at the actinostomial margin by two broad crescent-shaped processes or plates, which are articulated on the mouth-plates and appear to be the modified representatives of the inner or furrow spine on the adambulacral plates. These plates meet their correspondents in the median radial line and form a noticeable tract separating the first pair of ambulacral tube-feet from the buccal membrane.
The madreporiform body is situated on a distinct prominence, and at the margin of the abactinal surface. The slope of the prominence is covered with membrane and spinelets, in fact a continuation of the dorsal tegumentary structures. The striation is of great simplicity, consisting apparently of only two angulated furrows, one outside the other.
Colour in alcohol, ashy white, with a slight pinkish shade on the side of the ovarial regions, probably owing to the thinness of the plating there.
Locality.—Station 244. In the Mid-North Pacific, between Yeddo and San Francisco, near the meridian of 170° E. June 28, 1875. Lat. 35° 22' 0" N., long. 169° 53' 0" E. Depth 2900 fathoms. Red clay. Bottom temperature 35.3° Fahr.; surface temperature 70.5° Fahr.
Remarks.—This species is remarkable for the great length of the rays and the relatively short ovarial regions. It may be readily distinguished by the number of the rays, by the peculiar subcrescent or scimitar-shaped mouth-spines, by the armature of the adambulacral plates, and by the character of the spinulation of the abactinal plates.”
(Sladen 1889, 643-645)
