MONOGRAPH OF JAPANESE OPIIIUliOIDEA. 309 



Cryptopelia Clakk, 1909. 

 II. Oral sliields naked. 



Bathypectinura Clark, 1909. 

 B. Two tentacle scales to each pore. 



III. Genital slits entire. 



Pectinura Forbes, 1842. 

 Ophiopezella Ljungman, 1871. 

 Ophiochce'a Lütken, 1869. 

 Ophiarachnella Ljungman, 1871. 

 Ophiochasma Ljungman, 1871- 



IV. Genital slits divided into two secondary pores. 



Ophioderma Müller & Troschel, 1842. 



Ophioncus Ive«, 1889. 



Diopederma Clark, 1912. 



Ophiocryptus Clark, 1915. 

 This family is very uniform in its internal structure. The 

 peristomial plates are always triple, one of the three secondary 

 plates filling up the outer open angle formed by the other two, as 

 observed by myself in Ophiuroconis monolepis Matsumoto, Ophmrodon 

 grandisquama (Kœhler), Ophîurochœta mixta (Lyman), Ophiarachna 

 mcrassata (Lamarck), Pectinura anchista Clark, Bathypectinura goto I 

 Matsumoto, Ophiarachnella gorgonia (Müller & Troschel), Ophio- 

 derma januarii Lütken, 0. brevicauda Lütken, &c. In Ophiarachia 

 ' incrassata and Bathypectinura gotoi, the oral frames are very long 

 and have distinct, V-shaped grooves for the ambulacral ring canal, 

 while in the others they are short and have no distinct grooves 

 for the ring canal. In Ophioderma, the genital plate and scales of 

 the same side of a radius are soldered together at the middle, so 

 that the genital slit is divided into two secondary pores, an 

 inner and an outer. An important characteristic of the present 



