OCR Text |
Show 512 PROF. F. J. BELL ON THE GENUS ASTERIAS. [May 3, much as 3 millim. long, are autacanthid ; and their bases are surrounded by shorter spines or papilliform processes of the integument. Towards the tip of the arm the innermost row disappears. The large space between the outermost or third row, or that which runs along the lower portion of the side of the arm on either side, presents in its lower portion irregular and feebly-developed spines ; along the middle line of the back of the arm there runs an irregular row of spines or clumps of spines; and on either side of this there is a still more irregular row. The middle row is continued onto the disk, the centre of which is occupied by a clump of five autacanthid, more or less blunt and rounded tubercle-like spinous processes; at an equal distance from this central clump, and at the base of each ray, there is another clump, a little more irregular in character ; an accessory clump may be developed near the central one. The same clump-arrangement is exhibited all along the back of the arm, but varies within very wide limits, and only one spine may be developed. The whole integument is thick and granular, the madreporic body more or less prominent, pedicellariae rather rare. General colour light orange-yellow (after immersion in spirit for at least twenty-five years). 22=90, r=23 , 22=101, r=25. So far as we may judge from two specimens, the species will be found to exhibit considerable variation. It has the same general formula as has A. meridionalis, and, so far as one may judge from the diagnosis, A. scabra; from the former it may be at once distinguished by the less regular repartition of the spines of the abactinal surface, and by the complete absence of any bare interbrachial space on the actinal surface of the disk. I am quite unable to form any conception of A. scabra from Capt. Hutton's description. ASTERIAS INERMIS, n. sp. (Plate XLVII. figs. 2, 2a.) This species is also founded on a specimen collected by Mr. Good-ridge, and bears Ecuador as its locality. General formula 2aa'. It is remarkable for the very feeble development of spines on its abactinal surface, where, though all autacanthid, they form the merest projections. Rays five, broad at base, tapering rapidly but regularly; two rows of adambulacral spines; madreporic plate anechinoplacid, obsctue, quite at the margin of the disk ; spines of actinal surface short, slender, delicate and autacanthid. Of all the spines the longest are the adambulacral; but they do not exceed 2 millim. in length. Beyond these there is a row of spines, generally one only on each plate ; in the next outer row the spines are rather sharper and longer, and there are sometimes two on one plate. Beyond this the rows begin to get somewhat indistinct, and the spines still shorter. Plates carrying very short, white, tubercle-like spines are closely packed, without any apparent order, over the whole of the abactinal surface. |