264 



BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



A rocky bottom, or a bottom covered with highly calcareous organisms such 

 as calcareous algae, corals or lithothamnion, tends to induce the development of 

 very long and very stout cirri which, though flexible distally, are comparatively 



FIG. 298. 



FIG. 299. 



FIG. 301. 



FIG. 300. 



FIG. 302. 



FIG. 303. 



FIG. 304. 



FIG. 305. 



FIGS. 29S-305. 29S, VENTRAL VIEW OF THE CENTRODORSAL OF A SPECIMEN OF THAUMATOMETRA TENUIS FROM THE SEA OF JAPAN. 



299, VENTRAL VIEW OF THE CENTRODORSAL OF A SPECIMEN OF PENTAMETROCRINUS JAFONICVS FROM SOUTHERN JAPAN. 



300, VENTRAL VIEW OF THE CENTRODORSAL OF A SPECIMEN OF ATELECRINUS BALANOIDES (AFTER P. H. CARPENTER). 301. 

 LATERAL VIEW OF THE CENTRODOESAL OF A SPECIMEN OF NEMASTER LINEATA FROM BRAZIL, WITH THE ROSETTE AND TWO 

 RADIAL3 IN POSITION (AFTER P. H. CARPENTER). 302, VENTRAL VIEW OF THE CENTRODORSAL OF A SPECIMEN OF TlIAUMA- 

 TOCRINUS RENOVATU9 (AFTER P. H. CARPENTER). 303, LATERAL VIEW OF THE CENTRODORSAL, AND THE RADIAL PENTA- 

 GON WITH TWO RADIALS REMOVED, OF A SPECIMEN OF TROPIOMETRA TICTA (AFTER P. H. CARPENTER). 304, VENTRAL VIEW 

 OF THE EADIAL PENTAGON OF A SPECIMEN OF TROPIOMETRA PICTA; ONE OF THE BASAL RAYS (THE ANTERIOR IN THE FIGURE) 

 HAS BEEN REMOVED (AFTER P. H. CARPENTER). 305, THREE UNITED RADIALS FROM A SPECIMEN OF COMATin.A ROTALARI.V, 

 VIEWED FROM THE INTERIOR OF THE CALYX (AFTER P. H. CARPENTER). 



rigid proximally (fig. 309, p. 267) ; such cirri, most perfected in the species of Thalas- 

 sornetridse, are more or less characteristic of some or all of the species of Nemaster, 

 Capillaster, Comanthus, Himerometra, Heterometra, Oxyrnetra, Pontiometra, Dickro- 



