“Ilyphagus cristatus n. sp.
Figs. 23 a-23 c
Material. Weddell Sea, in 640 m: Station 68-1 (holotype, and 1 paratype, USNM 46824-5).
Description. Both types are incomplete posteriorly; the holotype measures 24 mm long for 21 anterior segments and about 2 mm wide in the anterior crested end, or widest part. It is cylindrical farther back and tapers slightly posteriorly. Segmental lines are lacking. The body is dull gray and appears to be smooth but under high magnification is seen to be minutely papillated all over. The bases of parapodia have large long papillae. An enveloping sheath is absent. The anterior end is truncate, and the oral apparatus is competely withdrawn. A vertical slit between the setal bases represents the oral aperture. The lateral membranes, or lips, can be pushed far out, indicating the presence of an extensile pharyngeal armature. This has been proved in the paratype specimen by making a ventrolateral incision back to the third setiger. At least eight short branchiae and a pair of thick palpi are visible; the processes are contracted so that a definite count of their total number is not possible.
The dorsum of the first three setigers is elevated and covered with coarse papillae in diffuse arrangement (Figure 23a) ; the sides and ventrum of the body are smooth. Each of the papillae has a bulbous base and terminal neck, ending in a distal pore (Figure 23b). Similar but smaller dorsal papillae are continued more posteriorly and more sparsely.
The first setiger bears the cage setae as paired slender tufts; each fascicle has about eight slender cross-barred setae. Parapodia are subbiramous beginning with the second setiger; the neuropodium is in the form of a translucent oval lateral path with vertical series of 3-4 neurosetae. One or two notosetae emerge from a minute notopodium. Notosetae are long, slender, and hairlike. Neurosetae are shorter, thicker, and obscurely cross barred basally and terminate in a falcate pointed tip (Figure 23 c) .
Remarks. Ilyphagus cristatus is distinguished from other species of Ilyphagus by its conspicuous dorsal crested region in the anterior region. The body lacks a mucous sheath. The oral organ consists of a pair of thick palpi and at least four pairs of branchiae.”
(Hartman, 1978)
