388 PHYLLACANTHUS BACULOSA. 



Secondary spines and papillae elongate, tapering, yellowish, with greenish 

 longitudinal stripe in middle. Primary spines nearly twice the diameter of 

 the test, gradually tapering towards extremity, often tinted, cupuliform ; 

 granulation in irregular longitudinal rows, with scattered larger spines along 

 body of shaft. Spines greenish, ringed with alternate bands of violet and 

 yellow. Test thin, somewhat compressed ; the general facies is similar to 

 Dorocidaris papillata. 



Australia ; Philippine Islands. 



Phyllacanthus baculosa 



! Cidariles baculosa Lam., 181 6, An. s. Vert. 



! Phyllaeanthru baculosa A. Ac, 1872, Rev. Ech., Pt. I. p. 150. 



PL P.f. 4, r,; PL P.f. S4-S8; PL P.f. U-2v a ; PL XXIV. f. 9; PL XXXV. f. 4. 



In all species of Phyllacanthus the normal number of primary tubercles 

 is early developed ; this number, rarely exceeding eight in each vertical row, 

 is already attained in specimens measuring 37 mm ', and the number is not 

 greater in specimens of double the size, even in this species, which is the 

 one of the genus where the primary tubercles are most numerous, being 

 smaller and more closely packed together than is usually the case in the 

 other species of the genus. 



The median interambulacral space is very broad, scantily covered by 

 minute miliaries carrying small papillae; so that this median space, even in 

 specimens covered with all their primary and secondary spines, has a very 

 denuded appearance. The scrobicular circle is elongate, elliptical, sur- 

 rounded by secondary tubercles, and less prominent than in species of this 

 genus, as the horizontal divisions between adjoining circles disappear almost 

 entirely, owing to the great reduction in the size of the dividing miliaries 

 and secondaries. The mammary boss of the primary tubercles is small, but 

 little prominent. The median ambulacral space is broad, with four well- 

 defined and well-sepai'ated vertical rows of miliaries placed within the two 

 outer rows of secondary tubercles forming the edge of this region. Two 

 of the inner rows are placed close to the outer rows of secondaries, the 

 other two inner rows are placed close together in the middle of the ambu- 

 lacral region. 



The genital plates are nearly of uniform size, the madreporic plate only 

 slightly largest; genital openings are situated one third the length of plate 

 from outer edge. Ocular plates very large, trapezoidal ; ocular openings small, 



