286 Verrill, Notes on Madiata. 



Liitken received his specimens from Cape St. Lucas through the Smith- 

 sonian Institution, and one from Acapulco from the Museum of Comp. 

 Zoology. 



The disk is small and the rays are slender, slightly tapering, 

 rounded-triangular. Proportion of radii as 1 or 8:1, The mature 

 specimens of average size have the greater radii S-V inches; the 

 smaller '5 ; width of rays at base "5. 



The interambulacral plates bear an inner double row of short, 

 crowded, papilla-like, alternately vmequal spines, and an outer row, 

 close to the inner, of similar form, but stouter and nearly uniform in 

 size. The plates are placed obliquely and each one bears on its inner 

 side a very small blunt spine, and a little more outwardly and to one 

 side, a much stouter one, which is flat, broad and truncated at the 

 end, but narrowed at base, and so arranged that the smaller ones 

 stand ■w'ithin and appear to alternate with them. On its outer por- 

 tion each plate also bears a still larger and stouter, but scarcely 

 longer, truncated spine, forming the outer row. The lower side 

 of the rays, outside of the interambulacral plates, is formed by four 

 or five rows of small, squarish, equal, and regularly arranged plates. 

 Beyond and joining these along the sides of the rays there is a row of 

 similar plates, but more than twice as large. Above these, and occu- 

 pying about half the width of the sides of the arms, there is a con- 

 tinuous longitudinal belt of pores, without intervening plates. Along 

 the middle of the arms there is a wide belt of irregular, angular, 

 crowded plates, larger and more convex than those of the lateral rows. 

 The plates are everywhere covered with similar, crowded, coarse, 

 rounded granules, which are largest near the ambulacral grooves. 

 The poriferous belts are covered with finer, rounded granules. The 

 madreporic plate is large, irregular in form, adjacent to the convex, 

 central, anal area. 



Color, in alcohol, light yellow or reddish. 



I am unable to find anything in the description of Ophidiaster 

 siituralis M. and Tr. by which it can be distinguished from this spe- 

 cies. Its origin was unknown, 



A somewhat larger specimen, without authentic locality, presented 

 to the Boston Society of Natural History by Mr. Horace Mann, dif- 

 fers in having the lateral poriferous region divided into two, for one 

 or two inches from the base of the rays, by a row of plates like those 

 of the dorsal series, with which they unite outwardly, forming thus 

 a wider region of plates without pores on the outer part of the rays. 

 This specimen has also three madi-eporic plates, regular and normal 

 in structure. The inner interambulacral plates, near the base of the 



