HABROCIDARIS SCUTATA. 81 



The remaining G or 7 abactinal ambulacral plates have one or two pairs o£ 

 pores and each of the larger plates carries a diminutive granular tubercle. 



The arrangement of the primary interambulacral tubercles is well shown 

 in PI. 54, figs. ^ 5, 7. The single primordial interambulacral actinal plate 

 carries from two to four minute granular tubercles, while that of II. anjaiica 

 (PI. 54, figs. 1, 3) carries a small primary tubercle. 



The pairs of pores of the actinal ambulacral plates are sunken in small 

 pits as in II. argentea and in the median line there is the larger spliEeridial 

 depression seen in that species. 



The tridentate pedicellariaj are not uncommon, especially near the am- 

 bitus. The valves (PI. 49, fig. 19) are very broad and flat, with nearly parallel 

 sides and almost truncate tip. The apophysis is narrow and forks widely at 

 the end, but the two divisions do not reach the margins of the valve. The 

 length of the valve is about .40 mm., while its width is nearly one-half as much. 



The ophicephalous pedicellariaa are very characteristic and are remarkable 

 for the very great constriction of the valves (PI. 49, fig. 17) just above the 

 middle and the peculiar widening and hollowing of the apophysis. The 

 articular loop (PI. 49, fig. 18) of the chief valve is relatively very large. The 

 valves are about .30 mm. in length, while the stalks are 6-8 times as long. 

 The upper end of the stalk (PI. 49, fig. 16) is very rough, obliquely truncate 

 and slightly constricted. 



The triphyllous pedicellarise are apparently wanting. 



The calcareous particles in the pedicels are straight rods (PI. 49, fig. 20) 

 with blunt tips. They are expanded at the middle and perforated there with 

 from one to four small holes. They are relatively very long (.40-.70 mm.) 

 and presumably lie horizontally in life, though they are more or less oblicjue 

 or even vertical in dried pedicels. 



The splijeridia (PI. 49, fig. 15) are proportionately large and are nearly 

 as long as wide. There is one in each ambulacrum, at the peristome, and it 

 lies on the surface of the test, in only a very slight depression. 



The type and only known specimen of this species was taken by the 

 " Blake " off Santa Cruz, Danish West Indies, in 580 fms. 



