OPHIUROIDEA 



225 



pletely covering the inner one, so that there is apparently only 

 one scale. Mouth shields about as long as broad, with a more or 

 less conspicuous outer lobe. Adoral shields narrow, meeting 



Fig. 127. — Ophiochiton ternispinus ; part of dorsal and oral side. x 5. 



inside the mouth shield. Five to six mouth papillae. Colour in 

 hfe unknown ; in alcohol brownish-grey or whitish. 



Only three specimens of this species are known at present. 

 One was taken by the " Porcupine " S.W. of Ireland (49° 12' N., 

 12° 52' W., 1577 m.), another by " IVIichael Sars " at 57° 41' N., 

 11° 48' W., 1853 m., and a third in the Davis Strait, 442 m. 

 (Wandel). 



[Family Ophiodermatid.^] 



A close granulation as a rule conceals completely the fine 

 scales of both dorsal and oral side of disk ; even the jaws are 

 mostly covered with granules, while the radial shields and the 

 mouth shields may be naked. Mouth papillae numerous, forming 

 a continuous series. A single series of teeth ; no tooth papillae. 

 Arm spines appressed. Second tube-foot inside the mouth edge. 



No representatives of this family are yet known from the 

 British seas, but four (five) genera are found in European seas, 

 all of these being more or less likely to occur also in the British seas. 



Key to the genera of Ophiodermatidce likely to he represented 

 in the British seas. 

 1. Two pairs of genital slits in each interradial space 



Ophioderma Miill. and Troseh. 

 Only one pair of genital slits in each interradial space . 2 



Q 



