126 SYNAPTIDAE. 
they were taken on the shores of Easter Island, December 20, 1904. The wheels 
Croke 45-65 » in diameter and the curved rods, which are very sparsely 
scattered and not very variable, are but 27-36 u in length. The small species 
of Chiridota need a careful revision based on the size, character, and distribution 
of the calcareous particles and when this is made the Easter Island form may be 
entitled to rank as a separate species, as the wheels seem to be much smaller 
than in typical rigida. 
Myriotrochus bathybius,' sp. nov. 
Plate 4, fig. 3. 
Length of preserved specimen, 33 mm.; diameter, 8 mm. Oral disk, 8 mm. 
across, with scattered yellow-brown papillae, most numerous near mouth, each 
about one fourth of a millimeter high. Tentacles twelve, each with three minute 
digitations on each side. Color, gray; outside of circle of tentacles there are 
seven dark spots lying between tentacle-bases. Calcareous ring stout, with 
distinct projecting points on the anterior margin of both radial and interradial 
pieces; the posterior margins are, on the contrary, almost straight. Stone-canal 
single, short, compact, free. Polian vessel, single, long. Genital glands well 
developed on each side. 
Caleareous particles consist of wheels alone, no deposits of any kind being 
found in the tentacles or oral disk. Wheels (Plate 4, fig. 3) very few and widely 
scattered; it may be that their scarcity is due to the abrasion of the epidermis 
during the long and rough journey to the surface in the trawl. Of the four seen, 
one had twelve, two had thirteen and one had fourteen spokes. Only two of 
these wheels were sufficiently uninjured to make the count of the teeth on the 
inner margin accurate; in a wheel with twelve spokes there were thirty-seven 
teeth and in one with thirteen spokes there were thirty-eight teeth. Evidently 
then the wheels in this species have typically thirteen spokes with the teeth 
three times as numerous. The most important feature of the wheels, however, 
is the hub which, as will be seen from the figure, is relatively large and has a 
circle of small oval perforations around the center. A few developmental stages 
of the wheels were found which explain this curious arrangement. As is the case 
with all wheels in the Synaptidae, the first beginning is a minute circular disk. 
Projections soon arise all around the margin and these lengthen into the spokes, 
which ultimately expand bilaterally at the tip, these expansions fusing with each 
other and forming the rim of the wheel. In the present species when the length 
* BabiBios = deep-living, in reference to the great depth at which it occurs. 
