58 . ART. 2. — H. MATSUMOTO r 



this species that, only two arms may sometimes be regenerated in 

 place of three, or one in place of two. 



This species can be distinguished very easily from the geno- 

 type, A. virgo. The arms are slightly less widened at the base 

 and keep their width for a less extent. The arm spines are only 

 one to each tentacle pore for over half the length of the arms, 

 while in the genotype, two are present even in the basal region. 

 Finally, the disk and arms are covered with fine scales instead of 

 granules. 



In this species, the widening of the arm bases is caused by 

 the widening of the vertebra?, and is not accompanied b}^ the ex- 

 tension of the generative glands, so that even in the widened part, 

 the arm covering of the dorsal side is in direct contact with the 

 vertebrae. I suppose that this condition is a generic character, 

 though there is no observation on this point in the genotype. 



Family 3. Gorgonocephalidse (Dödeeleix, 1911) mihi, 1915. 



Disk and arms covered by a thick skin, which contains 

 granules, very often beset with stumpy tubercles. Eadial shields 

 long, bar-like, forming a system of radiate ribs. The radial shields 

 and genital plates articulate with each other by means of a trans- 

 verse ridge on both the plates. Genital plates long and stout, 

 genital- scales small. Oral and adorai shields very small, the 

 former being often separated from the latter by a mosaic of sup- 

 plementary plates. Teeth and dental papilla?, often as well as oral 

 papilla?, similar, spiniform, acute, forming a clump or cluster at 

 the apex of each jaw. Peristomial plates entire, stout, soldered 

 w^ith the also very stout oral frames. Arms exceedingly long, 

 simple or branched, vertically coiled. Dorsal arm plates represent- 



