2 a NATURAL HISTORY BULLETIN. 



In the report on the Opiiiuroidea of the Voyage of the 

 Challenger, Mr. Lyman recognized about ninety species of 

 Amphiura. In subsequent papers by him and others, about 

 thirty additional species have been described. This very ex- 

 tensive assemblage of species is evidently capable of being 

 divided into several natural groups, in addition to the several 

 minor groups already separated by Mr. Lyman and others. 

 Indeed Mr. Ljungman, as long ago as 1867, set off a large 

 number of species as a natural generic group, under the name 

 of Amphipholis. At a still earlier date, Liitken had indicated 

 this and other natural sections of the genus, without naming 

 them. 



Mr. Lyman, however, did not recognize Amphipholis and 

 some other good divisions in an}' of his works, except as sec- 

 tions of the genus. 



Subdivisions of Amphiura. 



The species of Amphiura, as adopted hy Lyman, mostly 

 fall into four large groups, which seem to be natural divisions 

 of generic value. They are best characterized by the struc- 

 ture, number and arrangement of the mouth parts, as in most 

 other ophiuran families. A few aberrant species, not found in 

 American waters, must be referred to other groups. 



I. Amphiura (restricted). Type, A. chiajei Forbes. 



One apical or subapical mouth papilla. One (rarely two) 

 small, distal papilla (oral tentacle-scale); middle of jaw-edge 

 without papillae; mouth-slits gaping. Four to seven or more 

 (rarely three) arm-spines. Radial shields divergent. 



II. Amphipholis (restricted). Type, A. sguamata (or A. 

 elegans. 



Two small lateral mouth-papillae and one broad operculi- 

 form, distal one, forming a continuous series along the entire 

 jaw, and capable of nearly or quite closing the mouth-slits. 

 Radial shields in close contact. 



