Boone, Echinodermata, Cruises of "Ara" and "Alva" 137 



The side mouth shields are each a long, narrowed triangle, with 

 the narrowed ends meeting within. The mouth frame is typical 

 Ophiothrix. There are six small, acute teeth clustered in the 

 uppermost series at the apex. 



The ventral arm plate is nearly rectangular, being slightly 

 wider than long, broadly in contact through almost the entire 

 width. There is one tentacle scale present, extending about one- 

 half of the length of the lateral margin of the under arm plate 

 and situated anterior to the first and second arm-spines. The 

 tentacle scale is of medium size, narrowly oval, with pointed or 

 narrowed rounded apex. The tube foot has the surface beset 

 with numerous coarse, spiny granules. 



The side arm plates support near the base of the arm seven, 

 and farther along the arm, six arm spines in series. These spines 

 increase in length from the ventral to the sixth spine, the seventh 

 or most dorsal spine, when present, being shorter than the sixth 

 spine. The first, second and third spines are short, the fourth 

 spine medium, the fifth and sixth spines long, the seventh slightly 

 shorter and weaker than the sixth spine. The first, second and 

 third spines are each about one-third longer than its predecessor, 

 the fourth spine being nearly twice as long as the third, while the 

 fifth spine is one and two-thirds times as long as the fourth and 

 the sixth spine is twice as long as the fourth spine. The first, 

 second and third spines are very compressed, with the distal por- 

 tions spatulate and the lateral margins coarsely serrulate; the 

 fourth to sixth (or seventh) are more convex, with the distal 

 third of the lateral and terminal margins spatulate and serru- 

 late with a longitudinal series of fine sharp granules. 



The dorsal arm plates are wider than long, the length being 

 a little less than the width of the inner margin, or equal to about 

 one-half of the width of the widely rounded outer margin. The 

 lateral margins are oblique. 



Colour: See H. L. Clark, plate 15, figure 5. 



The present specimens, alcohol-preserved for several years, 

 have the disk spotted violaceous purple and the arms transversely 

 banded alternately with purple and cream. 



References: Ophiura longipeda, Lamarck, J. B., Hist. Nat. 

 Anim. sans Vert., 1816, t. II, p. 544.— DE Blainville, H. M. 



