28 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 8 



Oral shields about as long as broad, the inner half much wider than 

 the outer half, proximal margins broadly rounded, lateral margins con- 

 cave, distal and truncate. Adoral plates triangular, twice as broad as 

 long, widest distally, not quite meeting within. Jaws long and narrow. 

 Four oral papillae on a side, apical largest, rounded and blocklike, longer 

 than wide, tapering slightly proximally to give a triangular appearance 

 to some specimens; other papillae flat and rounded, longer than broad, 

 outermost slightly largest. Four bluntly rounded, broad teeth, lower- 

 most shortest, uppermost longest. 



Interbrachial spaces below covered with small overlapping scales 

 distally, but fewer proximally. Genital slits very large, bordered by large 

 and wide genital plates. First under arm plate triangular, longer than 

 wide, lateral margins deeply concave producing lateral lobes, distal mar- 

 gin convex. Succeeding plates rectangular, longer than wide, lateral 

 margins parallel, distal margin concave, proximal margin convex. Dis- 

 tally the proximal margins are produced in a right angle, and near the 

 arm extremities the plates become triangular. Basally the plates are in 

 contact, but distally they become separated by the side arm plates. Tenta- 

 cle scales, 2 on the basal pores, but the one on the under arm plate is 

 exceedingly small and soon disappears altogether. 



Color. — In dry specimens the disk and arms are light gray with faint 

 brown markings on the arms. Mouth parts and under arms light yellow. 



Types. — Holotype, AHF no. 6; 32 paratypes, 16 in M.C.Z. 



Type locality. — Station 823-38, 30-40 fms., San Juan Bay, Peru, 

 February 7, 1938. An additional paratype in the Museum of Compara- 

 tive Zoology from Station 826-38, 20-30 fms., San Juan Bay, Peru, 

 February 7, 1938, and one from Station 833-38, 8 fms., Independencia 

 Bay, Peru, February 10, 1938. 



Remarks. — This species lives in great numbers in a soft mud which 

 teems with small, white nematode worms, a most repulsive environment, 

 to which, however, it is well adapted by its small flat disk and long, very 

 slender arms. It is the first Amphioplus to be reported from the western 

 coast of South America and differs obviously from the 3 species from 

 the Panamic region described by Lutken and Mortensen in 1899. The 

 oral papillae and disk scaling are quite distinctive. The species has been 

 named philohelminthius because of its fondness for living with little 

 worms. 



