MONOGRAPH OF JAPANESE OPHIUKOIDEA. 11 



by two insignificant ridges between the pits for the articular peg 

 and the halves of the articular shoulder. In Ophiohyalus gotoi 

 the peristomial plates are usually double, with oblong halves, 

 but are triple in some interradii, the unpaired one being quad- 

 rangular and overlapping the paired ones. In Ophiostiha liidekii 

 the peristomial plates are double, often with unequal halves, 

 one of which overlaps the other. According to Lyivian, Ophioscolex 

 glacialis Müller & Teoschel has triple peristomial plates and 

 slender, cylindrical oral frames, without distal wings.'-* 



In Opliiohyrsa rudis Litnian, the internal structures of which 

 were studied by Lyman, the characteristics of the Ophiohyrs'mce 

 appear to be well realised. The whole oral skeleton is very com- 

 pact. The peristomial plates are entire, stout, intimately soldered 

 to the oral frames, which are also stout. The radial shields, as 

 well as the genital plates and scales, are comparatively small, the 

 plates and scales bounding only the outer part of the long genital 

 slits. The vertebrae are stout, short, more or less discoidal, the 

 wings being very thick laterally as well as dorsally ; a number of 

 basal vertebr«3 are especially discoidal, like those of the next two 

 families. The vertebral articulation is perfectly streptospondyline, 

 the articular peg being entirely absent. The articular shoulder is 

 divided into two long, stout, parallel condyles by a median groove. 

 The articular umbo is very stout, the downward prolongation con- 

 nected without any boundary with the upward prolongation of the 

 soldered mass of the articular knobs, so that the whole of the 

 umbo and knobs taken together is long dumb-bell shaped. In 

 Ophiosmilax mirabilis the vertebral articulation is essentially 

 similar, but there persists a well marked line of contact between 

 the articular umbo and the soldered mass of the articular knobs. 



1) This peculiarity will be discussed in a future paper. 



