OPHIACTIS KREBSII. 



Ill 



LIST OF SPECIMENS. 



Ophiactis Krebsii Lutkex. (Figs, lo, ii.) 



Ophiactis Krchsii Lutken. Addit. ad Hist. Oph., p. 126. 



Special Marks. — Commonly six arms and five arm-spines. A very 

 slight lobe on the outer side of the upper arm-plates. Four mouth- 

 papillo) to each angle of the mouth. 



Fijr. 10. 



Bescrijytlon of a Specimen. — Diameter of disk, 3.3"""- ; from outer 

 side of mouth-shield to outer corner of opposite mouth-slit, 1.6""°-; width 

 of ann without spines, .9"""' ; length of arm, 19™"° ; distance from outer 

 side of mouth-shield to inner points of teeth, to that between outer 

 corners of mouth-.'^lits, .8 : .8. Mouth-papillir, 

 four to each angle of the mouth, flat, tlun, 

 rounded, longer than broad. Teeth six, upper- 

 most one tapering and a little the longest ; the 

 rest flat, squarish, longer than broad, with a 

 cutting edge thickened at its middle point. 

 Mouth-shields much rounded diamond-shape, 

 with a little tail on the outer side ; length to 

 breadth, .4 : .3. Side mouth-shields stout, barely 

 meeting within. Under arm-plates about as long 

 as broad, octagonal, the inner lateral sides being 

 longest ; length to breadth (tenth plate), .4 : .4. 

 croaching a little below, projecting laterally a good deal. Upper arm- 

 plates oval, thick, slightly swollen, with a very small lobe on the outer 



Ophiactis Krebsii. (I'ppcr siUo ) 

 /, radial shield. 



Side arm-plates en- 



