MONOGRAPH OF THE EXISTING CEINOIDS. 



373 



The ventral or inner faces slope inward, forming collectively a funnel-shaped 

 space occupying the center of the radial pentagon (fig. 442, p. 351). These faces 

 are usually more or less divided up by delicate calcareous processes which extend 



Fm. 509. 



FI0.5U. 



FiO. 512 



Fio. 513. 



Figs. 509-513.-509, Dorsal -view of the badul pentagon or a specimen op Hatiikometra df.ntata from southern 

 Massachusetts. 510, DoBS-iL view of the radial pentagon of a specimen of Thavmatometra tenuis from the 

 Sea of Japan; the rosette has been broken away. 511, Dorsal raw of the radial pentagon of a spehmen of 

 Heliometra glaciaus after the bemoval of the rosette (after p. II. C-iRPENTER). 512, Dorsal mew of 



THE RADLVL PENTAGON OF A SPECIMEN OF PENTAMETROCRLNUS SEMPERI (AFTER P. U. CARPENTER). 513, DoRSAL \1EW OF 

 the radial PENTAGON OF A SPECIMEN OF PENTAMETROCRINUS JAP0NICU3 FROM SOUTHERN JAPAN. 



to meet the ventral face of the rosette, and collectively form a complicated net- 

 work, fining up the central funnel and often partially bridging over the ventral 

 radial furrow so as to convert it into an incomplete canal. In many forms these 



