216 ART. 2. — H. MATSUMOTO : 



Opliiothela Veruill, 1867. (=^ Ophioteresis Bell, 

 1892). 



Ophiopsammlum Lyman, 1874. 



Ophiogymna Ljungman, 1866. 



I Altkenia Brock, 1888. 



Gymnoloplius Brock, 1888. 



Ophio'oplms Marktanner, 1887. 



Ophiocetlüops Brock, 1888. 



Ophiosphcera Brock, 1888. 

 The internal structures of this family arc very uniform and 

 essentially similar to those of the Amphitiricke. In Ophiolhrix 

 nereidlna [(Lamarck), the oral frames are very stout, with very 

 well developed lateral wings for the attachment of voluminous 

 masticatory muscles. The peristomial plates are very small, entire, 

 transversely bar-like, with a very slight notch at the middle of 

 the outer border. The oral and dental plates are very stout, 

 together forming an X-shape in internal view. The teeth are also 

 very stout and quadrangular. The genital plates are very long, 

 bar-like, firmly fixed to the third to sixth vertebra, with a very con- 

 spicuous, ball-like articular condyle near the outer end to fit into 

 the large articular socket of the radial shield ; just anterior to the 

 articular condyle, there occurs a wing with a depression for the 

 attachment of the muscle between the genital plate and radial 

 shield. The genital scales are short, wide, flat, leaf-like, articu- 

 lating with the genital plate near the outer end of the latter. In 

 internal view the radial shields are extremely large and triangular, 

 has a very large articular socket at the outer adradial corner, and 

 are completely joined in pairs. As seen from the dorsal side the 

 first vertebra is very sliort and rhomboidal ; the second, which is 

 the shortest, almost linear transversely ; the thh'd like a cross, with 



