86 PROCEEDINGS OF THE ACADEMY OF [Feb., 



OPHIURODON gen. nov. 



Disk and oral angles, including oral^shields, closely covered with 

 fine granules. Four or five oral papillae on either side of each jaw; 

 outermost pointed inwards, stretching above next papilla. Teeth 

 flat, thin, with widened and often serrate end. Arms not very long, 

 widest at base, tapering outwards to the very slender tip. Ventral 

 arm plates very narrow, longer than wide, distinctly in contact with 

 each other. Vertebrae of distal arm joints often imperfectly divided 

 into halves by a longitudinal series of pores. Six or more arm 

 spines, long, flattened, hyahne, not appressed. Single tentacle scale 

 to each pore. 



The genotype is Ophioconis grandisquama Koehler, and it is worth 

 noting that a specimen of this species was recently collected at 

 Okinose (a submarine bank), in the Sagami Sea. 



OPHIUROCH^TA gen. nov. 



Disk closely covered with fine granules and sparsely beset 7.'ith 

 fine spines. Oral angles also granulated, but oral shields naked. 

 Numerous close-set oral papillae, of which outermost one is pointed 

 inwards, stretching above next papilla, which is the largest. Teeth 

 triangular and obtusely pointed. Arms not very long, rather stout, 

 stoutest at base. Dorsal, as well as ventral, arm plates well devel- 

 oped, widely in contact with each other. Six or more arm spines, 

 long, flagellate, opaque, not appressed. Two tentacle scales to each 

 pore, abraclial one overlapping base of lowest arm spine. 



The genotype is Ophiochceta mixta Lyman. 



Ophiurochceta differs from Ophiolimna in the following important 

 particulars: more numerous oral papillae, of which the outermost 

 one is not operculiform, but pointed inwards above the next papilla, 

 which is the largest; well-developed dorsal and ventral arm plates, 

 which are widely in contact with each other, two tentacle scales, 

 of which the abradial one distinctly overlaps the base of the lowest 

 arm spine; triple peristomal plates. Verrill considers that the 

 internal structures of 0. mixta are much like those of Ophiacantha; 

 but my own opinion is quite to the contrary. 



I have observed that the internal structures of Ophiuroconis 

 monolepis, Ophiurodon grandisquama, Ophiurochceta mixta, Ophi- 

 arachna incrassata, Ophiochiton fastigatus, Ophioplax lamellosa, etc., 

 belong to a common type. In them the peristomal plates are always 

 triple, consisting of two paired and one median secondary jDlates; 

 while in Ophiacantha, Ophiolimna, etc., the peristomal plates are 



