282 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



covered by the smooth coat of hairs typical of Schizocidaris ; it is 

 somewhat more open-meshed and, therefore, less shining than usual. 

 The collar as usual is very short, scarcely as long as the very inconspic- 

 uous milled ring. The apical spines are still in an immature condition. 

 The oral primaries are slender and straight, with a few rather coarse 

 lateral serrations. The third-fourth is transitional to the ambital 

 spines. , 



The scrobicular spines are only about 1 mm. long; they are thin 

 and flat with straight sides and straight cut ends. The marginal 

 ambulacral spines are in the main of the same shape, but narrower 

 and more slender; those near the peristome do not differ from the 

 others. The miliary spines are of the usual slender form. 



Only the small globiferous form of pedicellariae is represented. 

 This is rather characteristic, the valves and also the opening being 

 unusually short; the end tooth is very prominent (pi. 78, fig. 2). 

 They are in general very small, with the head scarcely more than 0.1 

 mm. long and the stalk about 0.3-0.4 mm. long. In spite of this 

 small size they are fairly conspicuous, partly because the head is 

 rather thick, partly because they are somewhat brownish. 



The spicules of the tube feet are of the usual spinous form. 



In color the primaries are white, with 2 or 3 fairly distinct broad 

 bands of pink. The secondaries and test are yellowish white. On 

 the denuded test the genital plates are seen to be of a faint greenish 

 color, the test being otherwise white. 



Remarks. — In spite of the young age of the specimen, the genital 

 pores being not yet developed, it offers such conspicuous characters 

 in its primary spines and in its pedicellariae that there can be no 

 doubt that it represents a distinct species of the genus Schizocidaris. 

 The characters of the test must be expected to differ in adult speci- 

 mens from what is found in the present young specimen; but the 

 characters of the ambital spines and of the pedicellariae will evi- 

 dently be quite sufficient for recognizing the species in its adult form. 



PSILOCIDARIS, new genus 10 



Diagnosis. — Apical system more than half the horizontal diameter; 

 peristome much smaller. Interambulacra with 6 or 7, ambulacra 

 with rather numerous plates; a rather conspicuous sunken median 

 line and fairly distinct grooves at the horizontal sutures in the inter- 

 ambulacra, but not in the ambulacra. Primary spines very long and 

 slender, without basal disk; apical spines without terminal widening. 

 Surface of primaries with short conical stumps. Secondary spines 

 slender, setaceous, not appressed. Globiferous pedicellariae with 

 slender valves in apparently both the large and small form. 



'<>i£iX6s=thin. 



