CLARK: BRITTLE-STARS. 269 



wedge of relatively coarse scales. Upper arm-plates broadly oval, 

 but proximally truncated, wider than long, in contact, except near 

 tip of arm, where they gradually become longer than wide and sepa- 

 rated from each other. Oral shields pentagonal, with proximal angles 

 rounded, about as wide as long; madreporite elliptical, much wider 

 than long. Adoral plates large and long, twice as wide at outer (radial) 

 ends as at inner, broadly in contact interradially, but radially well- 

 separated by first under arm-plate. Oral plates very small, not so 

 large as the big oral papilla they bear. Oral papillae two on each 

 side; one, the large block-like terminal one on the oral plate, the 

 other, a cylindrical (or slightly flattened), blunt, spine-like papilla 

 on the inrter end of the adoral plate; the papilla guarding the first 

 oral tentacle is very conspicuous and might easily be mistaken for an 

 additional oral papilla but it lies on the side of the jaw at a higher 

 level and is morphologically different. First under arm-plate quite 

 small, somewhat pentagonal, about as wide as long; succeeding plates 

 more or less tetragonal with rounded angles, lateral margins slightly 

 concave, longer than wide, broadly in contact. Side arm-plates 

 rather small, but each carries 5 (or, further out, 4) subequal spines 

 as long as the arm-segment; these spines are blunt, thickened at base 

 and only a little rough at tip. Tentacle-scale, usually single, well- 

 developed, situated on side arm-plate, close to the under arm-plate; 

 occasionally a second scale is developed situated on the lateral margin 

 of the under arm-plate; in young specimens and distally in adults, 

 the tentacle-scale may be wanting. Color, in life and in dried speci- 

 mens, disk, grayish usually with a few blackish spots near center; 

 arms and lower surface, pale yellowish; upper arm-plates on distal 

 half of arm often with a dusky spot, giving the appearance of indis- 

 tinct banding; arm-spines frequently dusky or with a dusky spot. 



An interesting variety, which seems to be rather rare, has the arms 

 annulated with red. This red is in the form of a very narrow line 

 along the proximal margin of the side arm-plates. The line does not 

 show on the ventral surface of the arms. It is well-marked dorsally 

 and in life is quite noticeable but in preserved material the red gradu- 

 ally fades and probably will ultimately disappear. This color-form 

 may be known as 



Amphiura vivipara annulata, var. nov. 



Hohtype — M. C. Z. 4,131, and Paratypc, M. C. Z. 4,132. With the 

 typical form; same date and collector. A single well-marked ex- 

 ample of this variety was found at the Tortugas, June, 1917. 



