CYSTOIDEA. 



295 



latter possesses long, free brachial processes in place of 

 recumbent arms. 



In another small section of the preceding great group are 

 the two well-known Silurian genera Hemicosmites and Caryo- 



Fig. 175. Cystideans. A, Cadaster acutus, showing the upper surface of the calyx, en- 

 larged, from the Carboniferous Limestone (after M'Coy). B, Codonites stelliformis, side view 

 of the calyx, of the natural size (after Meek and Worthen), from the Carboniferous Lime- 

 stone, c, Summit of the calyx of the same, enlarged. D, Side view of the calyx of Callocystites 

 Jewettii, of the natural size, showing the brachial furrows, from the Upper Silurian (after 

 Hall). E, Side view of the calyx of Apiocystites pentrematoides, showing one of the brachial 

 grooves, of the natural size (after E. Forbes). F, Side view of the cast of the calyx of Gom- 

 phocystites gfans, showing the inflated summit, and spiral brachial grooves, of the natural 

 size Upper Silurian (after Hall), a, Anal aperture ; p, Respiratory fissures, or rhombs ; 

 /, Recumbent arm, or pseud-ambulacrum. 



crinus, which agree with one another in having numerous 

 pores on each plate, these pores being separate externally, 

 but united in pairs by canals which run on the internal 

 faces of the plates. Hemicosmites (fig. 171) has an ovoid 

 calyx, the respiratory pores being disposed on each plate in 

 regular lines, and no arms are known. In Caryocrinus (fig. 

 172, A), on the other hand, the ovoid calyx is surmounted by 

 12-20 free jointed pinnulre arranged in three groups. There 



