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Show 1885.] DR. HUBRECHT ON A N E W PENNATULID. 517 noptilum are, however, less regularly arranged in distinct rows, the ventral surface is not in the same way wholly devoid of polyps &c. This is another reason for assigning a not unimportant intermediate position to the new genus. Echinoptilum will best be placed in Kolliker's section Spicatae, subsection Junciformes (/. c. ' Challenger ' Reports), and in that subsection it must form a new family, that of the Echinoptilidae, characterized by the important fact of the total absence of anything resembling an axis, present in all other Pennatulidae with the exception of certain species of the most primitive section, the Veretillese. In the very divergent section of the Renilleae also an axis is absent. The fact that certain species of Veretillum and of Cavernularia (another Veretillid) have an axis, whereas others of the same genus have not, is no argument to disqualify the new family ; as it must be borne in mind that this degree of variability is only exhibited by species of the most primitive section of the Pennatulids, in which the axis may well be said to make its first appearance, being insignificant and of variable dimensions in Veretillum cynomorium, Cavernularia glans, and Cavernularia liitkeni. Its total absence in the Renilleae also tends to prove that in the original stock from which the Pennatulids have sprung an axis was absent. This section is characterized by Kolliker (I. c. ' Monographie der Alcyonarien,' 1872, p. 263) as " very different from the other Pennatulids in its possession of a more simple internal structure," and related to the lowest Veretillidse. It is thus the more remarkable to find an axis to be totally deficient in the new genus,which already so clearly shows points of agreement with those groups that are generally recognized as more highly developed, and in which an axis is present-sometimes even very strong and massive-without a single exception. EXPLANATION OF THE PLATES. PLATE XXX. Fig. 1. First specimen of Echinoptilum macintoshii, lateral view, enlarged about 1£ times : I, rhachis; s, stem. 2 & 3. Second specimen of the same, seen from below (2) and in lateral perspective (3), enlarged \\ times: r, rhachis; s, stem. In fig. 1 the median ventral depression at the lower extremity of the stem is visible ; in figs. 2 and 3 the median ventral furrow on the rhachis. 4. Front view of a polyp-cell and its calcareous spicules, more considerably enlarged. 5. Lateral view of the same. The polyp represented as emerging from the cell is entirely imaginary, and only meant to indicate the position of the opening in the cell. 6. Dorsal, and Fig. 7 ventral, view of the rhachis of specimen fig. 1, exactly reproducing the position of polyp-cells and zooids on these two surfaces. The ventral furrow on the lower part of the rhachis is plainly visible in fig. 7. 8. Part of a transverse section, intended to show the perforation of the wall of the polyparium z, corresponding to a zooid. d I, the longitudinal dorsal channel; sp, spicules in the integument. P R O C ZOOL. Soc-1885, No. XXXIV. 34 |