378 ART. 2. — H. MATSUMOTO : 



groups and not directly related to each other, not to mention that 

 the Ophîotrichidœ are the most highly specialised of the Gnatho- 

 phiurida. 



It appears to me to be noticeable that in those forms, in which 

 the masticatory apparatus is well developed, the oral papillae are 

 liable to reduction. In Ophiacfis, Ophiopiis, Hemipholis, the Am- 

 pliiodia-gvoxï^, &c., the papilla3 which arise from the adorai shields 

 are absent. In OpMopliolis and the Ampliiura-^oxï^, the oral 

 plates are almost free of papillae. In Ophiopsila {Ophiocomidœ), the 

 outer oral papillae are strongly reduced. And finally, the Ophîo- 

 trichidœ entirely lack the oral papillae. This fact probably has a 

 certain biological meaning. 



The interrelationships of the Gnatliophiurida may be shown 

 approximately as follows. 



Ophiotrichidse 



/ . 



/ - 



Ampliinrinœ 



/ 

 Ophiactiniuas 



Amphilepididse 



Ophiacanthidse 



■u-ith only horizontally 

 flexible arms. 



The Chilophiurida are very extensive and divergent, and it is 

 very difficult to make out their interrelationships clearly. Certain 

 genera of the Ophîolepididœ, e.g. Astrophiura, Ophiomisidium, Ophio- 

 mastus, &c., and Ophiomuslum, are frequently looked upon by 

 certain authors as very primitive. I can agree with these authors, 



