In _Triarthrus_, _Neolenus_, and _Ptychoparia_ they project ahead of the cephalon, emerging quite close together under the front of the glabella, one on either side of the median line. In _Cryptolithus_ they turn backward beneath the body, but since only three or four specimens are known which retain them, it is possible that other specimens would show that these organs were capable of being turned forward as well as backward. The proximal ends of the antennules being ball-like, it is probable, as Doctor Faxon has suggested to me, that these "feelers" had considerable freedom of motion. The antennules of _Triarthrus_ are apparently somewhat less flexible than those of the other genera, and have a double curvature that is seen among the others only in Ptychoparia. The proximal end of an antennule in _Triarthrus_ is a short cylindrical shaft, apparently articulating in a sort of ball-and-socket joint. The proximal end in the other genera is still unknown. The points of attachment in _Triarthrus_ seem to be under the inner part of the second pair of glabellar furrows. In _Cryptolithus_ they appear to be beside the anterior lobe of the glabella under what have long been known as the antennal pits. In the other genera the location is not definitely known, but in _Neolenus_ it seems to be under the dorsal furrows near the anterior end of the glabella. Viewed from the under side, the point of attachment is probably always beside the middle or anterior part of the hypostoma, just behind the side wings.