WEST INDIAN STARFISHES 167 



mostly blunt spinules, which, are not appressed. Thus the lower 

 surface appears unusually rough and spinose. 



The adambulacral plates bear an inner group of three com- 

 pressed, rather slender spines on the prominent inner angle ; the 

 median one, which stands farther in, is curved and larger than 

 the others. Outside of these there are two very unequal spines, 

 nearly side by side; the adoral one is large, stout, a little flat- 

 tened, subtruncate, and much longer than the other, which is 

 usually flat and slightly spatulate. Sometimes a second small 

 one stands by its side. External to these there is a row of three 

 or four slender spinules. There is a small group of three or 

 four small, spinulated, interactinal plates. 



The dorsal paxillse are rather large, regularly stellate, and 

 when the spinules are extended they interlock and cover the sur- 

 face closely, but the spinules are often folded up in a compact 

 fascicle, exposing the large papular pores. Their spinules are 

 rather long, clavate or capitate ; about eight to ten marginal ones 

 surround one, or less frequently two or three central spinules of 

 about the same form and size, or a trifle larger, but not spini- 

 form. At the bases of the rays and on the adjacent parts of the 

 disk they become larger, and many have four to eight central 

 clavate spinules and twelve to sixteen around the margin. The 

 radial paxillge do not form regular transverse rows, but about ten 

 to twelve can be counted across the ray proximally. They are 

 as large along the middle of the rays as laterally. A few very 

 small ones surround the minute dorsal pore. 



Madreporic plate is nearly concealed by the paxillas. Ocular 

 plate is narrower, longer, less swollen, and less deeply bilobed 

 than in A. articulatus. 



Variations. 



This species is decidedly variable, as shown by Liitken, and 

 well deserves the name he gave it. 



A well-grown specimen from Florida (No. 259, Yale Mus.) oth- 

 erwise normal, is peculiar as to its dorsal spines. On some of the 

 rays several of the proximal plates carry three or four small 

 spines, and in one case the first plate has six such spines, while 

 its mate has only three. On some of the other rays both have but 

 one spine. These additional spines have mostly been produced 



