306 A. E. Verrill — North American Ophiuroidea. 



cula; while in the latter the few slender and widely separated 

 mouth-papilljB cannot close the slits, but always leave them widely 

 open. This difference is doubtless directly correlated with impor- 

 tant differences in their mode of feeding and nature of their food. 



Subdivisions of Amphiuea. 



The species of Amphiara, as adopted by Lyman, mostly fall into 

 four large groups, which seem to be natural divisions of generic 

 value. They are best characterized by the structure, number and 

 arrangement of the mouth jsarts, as in most other ophiuran families. 

 A few aberrant species, not found in American waters, must be 

 referred to additional groups (V, VI, etc.). 



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



One apical or subapical oral papilla. One (I'arely 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. AmphiphoUs (resti'icted). Type, A. squamata (or A. elegans.) 

 Two small lateral oral papillae and one broad, operculiform, 



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. 



III. Amphiodia Verrill, 1899a. Type, A. p>y'lchella (Lym.). 

 Three (rarely four) small subequal oral papillas, none of them 



operculiform ; they form a regular series, attached mostly to the 

 side jaw-plate. No distal oral tentacle-scales. Three (rarely four) 

 arm-spines. Radial shields often more or less joined, 



IV. AmpMopliis Verrill, 1899a. Tj^dc, A. tumida (Lym.). 

 Four or five small unequal oral papillae, none operculiform, usually 



arranged in a discontinuous series, of which the outermost, at least, 

 arises from the adoral shield and is really a distal oral tentacle-scale. 

 Arm-spines three (rarely four). Radial shields generally quite sepa- 

 rated. Disk scales naked. 



V. ParampMxira Koehl. Kcehler has recently established a new 

 genus, Paramphiiira, for A. pxmctata Forbes and A. hellis, var. 

 tritonis Hoyle. 



It is distinguished by having a pair of large supplementary scales 

 or plates, proximal to the adoral plates. There are two small oral 

 papillae. 



VI. Ctencmiphiura Ver., gen. nov. Another special group is 

 represented by A. maxima Lym. 



