126 SYNAPTIDAE. 



they were taken on the shores of Easter Island, December 20, 1904. The wheels 

 are only 45-65 y. in diameter and the curved rods, which are very sparsely 

 scattered and not very variable, are but 27-36 fi 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, 1 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 

 digit at ions 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. 



Calcareous 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 



1 /?a0i>/?ios = deep-living, in reference to the great depth at which it occurs. 



