22.6 



II. MATSUMOTO : 



each radius ; they arc confined in occurrence to the pentagonal body. 

 Each dorsal plate with a pair of lateral arm-plates which arc greatly 

 modified, in relation to their being contained within the pentagonal 

 body. The two first lateral arm -plates belonging to different but 

 directly adjoining radii arc apposed to each other in their distal parts 

 and outside of the second interradial. Distal edges of successive 

 lateral plates form a continuous line forming interradial border of the 

 pentagonal body. This border is slightly concave in the middle 

 and is margined by a scries of soldered papilla:, which arc evidently 

 modified arm-spines of the modified lateral plates. These papilla? 

 grow longer towards the middle of interradial border, there attaining 

 a length about equal to the width of the lateral plate they belong 

 to. They number 3 or 4 to each lateral plate. 



The ventral interbrachial surface of the pentagonal body, with the 

 exception of the peripheral zone, is covered with a thin skin containing 

 fine, delicate, transparent, closc-sct and polygonal or circular scales. 

 The peritoneal cavity and genital glands can be discerned through the 

 skin ; both apparently extend into the arm bases. Genital bursa:, 

 plates and scales are absent, while the genital openings arc in- 

 visible. There is only a single oral shield, the madreporite, which is 

 irregularly triangular in shape and so small and transparent as to be 

 scarcely perceivable unless the specimen be dried. It is separated from 

 the adorai shields by a space. The adorai shields (erroneously called 

 "genital plates" by Si. ADEN) arc long and narrow, with free inner 

 ends. The oral plates (again erroneously called " side mouth shields," 

 i. e. adorai shields, by SLADEN) are large and stout. A single tooth 

 (" apical mouth papilla: " of Sladen) is present at the apex of each 

 jaw, directed somewhat upwards. There occur no dental or genuine 

 oral papillae; but there exist six or seven papillae ("mouth papillae," 

 i. e. oral papillœ, of Sladen) to each jaw ; they are deeply situated 

 within the oral slits, are directed upwards, and lie on the whole on a 

 higher level than the single tooth, though the most apical two or three of 



