146 ART. 2. — H. MATSUMOTO: 



least specialised among the Gnathophiurida, and stands next to 

 the Laemophinrida. 



In Amphiactis umbonata Matsumoto, the genital plate and radial 

 shield articulate with each other by means of a hemispherical 

 articular condyle of the former and a large articular socket of the 

 latter, the former being entirely free from the basal vertebra?. 

 The genital scales are flat and thin, articulating with the genital 

 plates near the outer end. The peristomial plates are simple and 

 very large. The oral frames are small and entire, without well 

 developed lateral wings. The oral plates are long and slender in 

 internal view. The dental plates are absent. According to Lyman, 

 the internal structures of Amphilepis norvegica Ljungman, 1860, 

 appear to be essentially similar to those of the above mentioned 

 species, save that the peristomial plates are somewhat smaller and 

 the dental plates are present. 



A'inphilepis tenuis Lyman. 



Ampldlepis tenuis: Lyman, Bull. Mus. Comp. Zool., VI, Pt. 2, 1879, p. 

 35, PI. XYI, figs. 432-434; Lyman, Rep. Clialleuger, V, 1882, p. 151. 

 Southwards from Boshii ; 1,875 fathoms (Lyiman). 



Amphiactis Matsumoto, 1915. 



Disk covered with imbricating scales, radial shields moderate- 

 ly large. Four or five oral papilla? on either side, unequal in size, 

 arranged almost in a continuous series. Teeth arranged in a single 

 vertical row. Peristomial plates entire, very large ; oral frames 

 slender and without lateral wings. Arms long and slender, only 

 horizontally flexible. Distal vertebrae often imperfectly divided into 



