1 42 H. Rathhun — List of the Brazilian Echinoderms. 



skin is nearly smooth, of a brownish yellow color, and with two 

 rows of large purplish brown spots along the dorsal side, and many 

 smaller, darker spots scattered promiscuously, but most numerous 

 on the lateral and dorsal surfaces. The skin is further covered with 

 a net-work of fine I'eticulations of slight purplish color, giving it a 

 tessellated appearance. A narrow line of the same color extends 

 through the middle of the interambulacral spaces. 



The ambulacral zones are of sub-equal width, and about two to 

 three times as broad as the intervening spaces. The suckers are 

 moderately abundant, slightly more numerous in the median ventral 

 than in the other zones, but without regular arrangement, except 

 toward the posterior extremity, where there are two rows to each 

 zone ; near the middle of the body, about four to five range across 

 each zone. Around the anus there are five clusters, each of five to 

 eight, more or less pointed papillae. 



The plates of the skin (with suckers) are very numerous, and of sev- 

 eral very distinct kinds. The commonest kind is the smallest; minute, 

 flattened, regularly oblong-elliptical in outline, with six small, elongate 

 perforations, arranged in two rows. Four other kinds are common : 

 (1.) A larger, heavier ])Iate, with the margin forming four strong 

 lobes, to each of which corresponds a large, cii'cular perforation, 

 each lobe in turn being usually divided into two or three smaller 

 lobes, bearing a large rounded tubercle; two or three similar tiiber- 

 cles occur between the perforations. This plate may be much 

 enlarged, the number of perforations increasing in proportion. (2.) 

 A table-shaped plate, smaller than the last, and composed of a nar- 

 row, upper rim of a squarish outline — a square, with slightly curved 

 sides and rounded corners — pierced at each corner by an oval hole, 

 or seldom with a complete circle of perforations ; and four legs, which 

 begin just within the corner perforations, and bend strongly inward 

 for one-half their length, to where they are banded together; below 

 this they are straight, and closely joined at the base, leaving only a 

 small central perforation, surrounded by ten to twelve pointed, diver- 

 gent tubercles. (3.) A slender, flattened, elongated plate, bulging 

 strongly outward on both sides at the center, and tapering slightly 

 to the ends, which are also enlarged and rounded ; on each side of 

 the center there is an elongated perforation, and the rounded ends 

 have one to three small holes. This plate is sometimes broadened 

 and bears a row of perforations along one-half or all of one side. 

 (4.) A rather small cage or basket-shaped plate, of nearly globular 

 form, coming probably from the suckers. 



