124 ART. 2. — H. MATSUMOTO : 



includes Opliîoleda minima Kœhlee, 190ß {=^ Ophioplinthaca occlusa 

 Kœhlee, 1907), Ophiomitra hàbrotata Clark, 1911, &c. The 

 differences between these two groups may be given as follows : 

 Genuine Ophiothamniis : — Disk marked out into five brachial 

 lobes by deep interradial notches of the interbrachial 

 borders, and strongly puffed out interbrachially ; disk scales 

 fine ; radial shields not perfectly joined, but in contact with 

 ■ each • other only at the outermost parts (except in 0. 

 remotus)', oral shields very small, separated from the first 

 lateral arm plates by the adorai shields, which are very 

 large ; interbrachial ventral surfaces large, covered with 

 numerous fine scales ; arms very slender, composed of long 

 and slender joints ; arm spines not serrate, the lowest one 

 being never hook-shaped ; ventral arm plates very small, 

 much narrower than the corresponding arm joint ; genital 

 bursas very rudimentary, being represented merely by the 

 creases . between the interbrachial ventral surfaces and the 

 arm bases ; genital plates very closely set in radial pairs, lying 

 above the basal vertebrœ ; genital scales absent ; generative 

 glands covered by a membrane, which contains fine scales ; 

 peristomial plates triple ; distal vertebrae incompletely 

 divided into halves by a longitudinal series of pores. 

 So-called Ophiothamnus : — Disk not distinctly lobed ; disk 

 scales coarse ; radial shields joined in pairs along nearly 

 the entire length ; oral shields large, in contact with the 

 first lateral arm plates ; adorai shields large, lying entirely 

 proximal to the oral shields ; interbrachial ventral surfaces 

 small, covered with rather few coarse scales, of wliich two 

 or three are large and conspicuous ; arms stout at the 

 base, composed of short and stout joints ; arm spines usually 



