WEST INDIAN STARFISHES 79 



The dorsal surface is covered irregularly with small, short, 

 blunt or clavate rough spines. These stand partly isolated, part- 

 ly in little irregular rows of two to six. These rows run in 

 various directions, but on the rays mostly obliquely or trans- 

 versely to the ray, but without order. The concealed plates are 

 irregularly lobed and reticulated, so as to leave rather large 

 isolated papular pores, which are scattered over the whole dorsal 

 surface, and also fonn a regular row between the two rows of 

 marginal plates, where they are either single or two together. 

 Madreporic plate, which is nearer the center than the margin, is 

 small, oval, with fine gyri, and surrounded by small obtuse spines. 

 Dorsal pore is small, surrounded by very small spinules. 



The superomarginal plates are irregularly three-lobed or four- 

 lobed, emarginate on both edges for papular pores. Each one 

 bears about three or four small erect spinules like those around 

 them, and irregularly placed. 



Inferomarginal plates are prominent, beyond the upper ones, 

 and form the margin. They have marginal notches between 

 them. Each bears a horizontally projecting, single, outer mar- 

 ginal row of about five or six closely placed, slightly divergent, 

 and only a little unequal, oblong, blunt spines. Above these, 

 on the upper side, there is another row, corresponding in number, 

 but not half so long, of small, acute spinules. 



The under side of these plates, as seen through the thinner 

 dermis, is transversely oblong, with the lateral margins slightly 

 incui'ved, and with a small groove and marginal ridge at the 

 inner end ; the ridge may end in a slight tubercle at one or both 

 ends. The rest of the surface is covered with minute rounded 

 elevations. 



The interactinal plates are easily visible, and mostly without 

 spinules. They form oblique forked rows running from the 

 marginals to the adambulacrals. The rows are separated by 

 spaces covered only by the dermis, but the plates in each row 

 are in close contact or slightly imbricated. 



These rows or series of plates start from an angular plate op- 

 posite the suture between two inferomarginals. This is joined 

 ado rally by two (sometimes one) long-ovate, narrower plates, 

 with the larger end centered; each of these is followed by two 



