340 AET. 2. — H. MATSUMOTO : 



• 



The arm length varies from six to eight times the diameter 

 of the disk. In the smaller specimens, the arm spines are less 

 flattened ; and in those of less than about 4 mm. across the disk, the 

 secondary supplementary pieces on the arms are almost invisible. 



This species differs from the genotype, 0. didydisca Claek, 

 in the shape of the dorsal arm plates, in the less well developed 

 secondary supplementary pieces, in the smaller and less distinct 

 radial shields, and in the smaller arm spines of the basal joints. 

 Further, schizogonic reproduction has not been observed in this 

 species, though I have examined many small specimens. On the 

 other hand, 0. marktanneri, as well as the genotype, resembles 

 Ophionereis dubia (Müllek & Teoschel, 1842) in lacking the 

 genital papillœ, but differs from it chiefly in the presence of 

 secondary supplementary dorsal arm plates, and in the much 

 narrower arms. 0. marktanneri is by no means near to Ophionereis 

 porrecta Lyiman. I could mention some more differences than those 

 enumerated by Kœhlee between these two species, but it will 

 not be necessary to do so here. 



This beautiful species is one of the most common ophiurans 

 about Misaki, living under stones and rocks. 



Family 5. Ophiocomidae Ljungman, 1867. 



Disk covered with fine granules or by a naked skin, some- 

 times bearing scattered spines. Radial shields very stout, but 

 externally invisible, those of a pair widely separated from each 

 other. Four to six oral papilla3 on either side, the outermost 

 one being pointed inwards above the next one. Dental papillae 

 well developed, forming a vertical clump at the apex of each jaw. 

 Teeth quadrangular and very stout. Peristomial plates double. 



