ÏO ART. 2. — H. MATSUMOTO : 



The difference between the Ophiomyxinœ and Ophiohyrsinœ 

 appears to me to be very sharp, especially in the internal struc- 

 tures. In Ophiodera anisacantha, the peristomial plates are triple, 

 the unpaired one filling up, Hke a wedge, the outer open angle 

 formed by the paired ones, wliich are very long and boot-shaped. 

 The oral frames are stout, with a distinct groove for the ambula- 

 cral ring canal. The first few vertebrae are very short, with very 

 thin wings. The genital plates are very slender, articulating with 

 the genital scale at a distance inwards from the outer end. The 

 articulation of the genital plate and radial shield is very simple, 

 without any articular condyle or pit. Each vertebra outside of 

 the base is composed of a slender body and very thin wings. 

 The vertebral articulation is zygospondyline. The articular peg is 

 well developed, connected with the halves of the articular shoulder 

 by a short, narrow ridge, so that the whole trio is shaped like an 

 M, of which the upper open angle corresponds to the pit for the 

 articular umbo and the lower open angles to the pits for the 

 articular knobs of the next vertebra. The articular umbo is very 

 stout, elongated rhomboidal, while the articular knobs are rather 

 feeble, separated fi'om each other by the pit for the articular peg. 

 In Ophiomijoca flacclda Müller & Teoschel and 0. austrcdis 

 LüTKEN, the peristomial plates are double, nearly soldered together ; 

 especially in very small specimens of the last species, the double 

 plates are very firmly soldered together, so as to appear almost 

 entire. The vertebral articulation of the last species is rather 

 peculiar : the trio of the articular peg and halves of the articular 

 shoulder are closely set side by side, so as to appear like a united 

 mass leaving a furrow-like pit for the articular umbo of the next 

 vertebra above them ; the articular umbo is very prominent, wMle 

 the articular knobs are scarcely developed, being represented only 



