CHARACTERISTIC DEEr-SEA TYPES. POLYPS. 



143 



the favorite abode of many kinds of ophiurans, and of sea- 

 anemones, which are attached to the bare portions of the axis. 

 We may mention among them a hivge species of Anthoptilum 

 (Fig. 452), and a species of Balticina. (Fig. 453.) The extrem- 

 ity of the axis of many of these wands is frequently laid bare 

 by injuries. These naked spaces, as has been observed by Pro- 

 fessor Verrill, are nearly always occupied by a peculiar Actinia 

 (Actinauge), of which the sides of the flat base spread out 

 longitudinally so as to wrap around the axis 

 of the polyp and meet on the opposite side, 

 forming a regular sheath by the coalescence 

 of opposite edges. (Fig. 454.) The base of 

 adjoining Actiniae coalesces in the same man- 

 ner, and thus forms a continuous covering 

 over the dead polyps. 



Professor Kolliker, who examined the 

 " Challenger " collection of Pennatulse, came 

 to the conclusion that the deeper portions of 

 the Pacific and Atlantic oceans contain very 

 few Pennatulye at a certain distance from 

 shore, and that these appear to have a wide 

 distribution along the shores ; the higher 

 groups especially being characteristic of shal- 

 lower water, while the simpler forms, the representatives per- 

 haps of an extinct fauna, inhabit the greater depths. 



The gorgonians are well represented in deep water by pecu- 

 liar genera, of which the base is specially adapted for living in 

 the mud, where it branches in all directions penetrating the soft 

 ooze as if with roots ; all the shallow-water species having usu- 

 ally a flat expansion of the base, by which they attach them- 

 selves to solid substances, rocks, mollusks, etc. 



Many of these gorgo- 

 nians are of an orange or 

 reddish orange color ; and 

 the most characteristic of 

 these is the elegant Dasy- 

 (jorgia Agassizii (Fig. 



Fig. 455. — Dasygorgia Agassizii. 1. (Venill.) 455), a plumOSe UlUch- 



Fig. 454. — Actinauge 

 nexilis. ^. (Verrill.) 



