194 ART. 2, — H. MATâUMOTO : 



pentagonal, with nearly straight interbrachial borders ; while in the 

 larger ones the disk is swollen and the interbrachial regions bulge 

 out more markedly. The radial shields do not take part in this 

 .bulging process, and are consequently deeply sunken, while their 

 distance from the centre of the disk is not much greater than in 

 the smaller specimens. The radial shields are distinctly separated 

 in the smaller specimens, but more or less meet with each other 

 in the larger ones. The colour in alcohol, as in life, is also 

 variable. Some specimens are gray or yellowish gray, and spotted 

 on the arms with dark gray ; others are dull yellow, with some 

 disk scales gray ; the radial shields are usually light yellow, 

 hemmed with dark gray. Specimens with coarse and irregular 

 disk scales are darker in colour. 



Amphiura (Foebes, 1842) Verrill, 1899. 

 Syn. OpMonephthjs Lütken, 1869. 



I look upon Ophionephthys Lütken as a synonym of Amphiura 

 s. str. The reduction of the disk scales which is a characteristic 

 of Opliioneplithys is also observed in Amphiura acrystata, as well as 

 in some Amphiura formerly referred to Hemilepis, while the 

 absence of the tentacle scales is characteristic of certain Amphiura 

 formerly referred to Ophiopeltis. There is not a single character 

 by which Ophionephthys can be satisfactorily distinguished from 

 Amphiura. 



Key to Japanese species of AmjiMura. 



A — Tentacle scales present. 



a — Two tentacle scales to each pore. 



