68 PROCEEDINGS OF THE ACADEMY OF [Feb., 



and more acute. Deep in oral slits, on either side of each jaw, occurs 

 an additional papilla, which is conical and acute. Five teeth, all 

 obtuse, except uppermost, which is acute. 



Arms slender, flattened, uniformly tapering distally. Dorsal arm 

 plates large, fan-shaped, twice as wide as long; inner sides slightly 

 convex, forming an obtuse angle within; distal margin decidedly 

 convex; outer angles rounded; successive plates separated by 

 lateral arm plates, except the basal two or three, which are in contact 

 with each other. Lateral arm plates low, not very prominent. 

 First ventral arm plate small, divided into two secondary plates, 

 of which the inner one is triangular and the outer quadrangular; 

 those following, large, hexagonal (except second, which is pentag- 

 onal), much wider than long, widest at outer lateral angles, with 

 concave lateral sides, distal and proximal margins slightly convex; 

 swollen along the outer margins and especially distally, so that 

 arm appears keeled along ventral median line. Arm spines three, 

 subequal, about as long as corresponding arm joint (uppermost 

 slightly longer), cylindrical, tapered and blunt. Two flat, oval 

 tentacle scales to each pore, but sometimes three on the first. Color 

 in alcohol: white. 



Two specimens; Sagami Sea. 



The internal structures of the present species are essentially 

 similar to those of Amphilepis norvegica Ljungman. The peristomal 

 plates are simple, very large. The oral frames are entire, without 

 lateral wings. The oral plates in internal view are very slender and 

 long. The dental plates are absent, so that the teeth arise directly 

 from the oral plates. The genital plates are free from, instead of 

 being fixed to, the basal vertebrae. The genital plate and radial 

 shield of either side of a radius articulate with each other bj^ means 

 of a conspicuous, ball-like condyle on the former and of a large 

 socket in the latter. The genital scales are flat, thin, leaf-like. The 

 vertebrae are very slender, the distal ones being incompletely divided 

 into halves by a series of pores. The first five characters and the 

 last are rather Lsemophiuridan, but the other two, the sixth and 

 seventh, are strictly Gnathophiuridan. 



Family 2, AMPHIURID^ Ljungman, 1867 (emend.). 

 (Characters as given in key, p. 66.) 



Key to suhfmnilies of Amphiuridce. 



A — No paired infradental papillae Ophiactinin.e. 



AA — Paired infradental papillae present Amphiurin^. 



