487 
ARTIFICIAL. KEv TO THE GENERA OF NORTH-AMERICAN HOLOTHURIANS. 
Calcareous deposits in skin, DUET of anchors and, plates 
Sigs. 32 and P4) Se aa pun Synapta 
Without respiratory trees | Calcareous deposits in skin, wheels with 6 a bs Hh col- 
(Synaptidz) | lected in little heaps .. . Chiridota 
Calcareous d cn in skin, scattered wheels with about 19 
| spokes . Ps cos ls eda ue. v... V Mirobodhis 
( Tentacles simple, unbranched; calcareous ring without pos- 
Without pedicels or papilla 4 terior prolongafions o = GR e 4 1.5 ee. Eupyrgus 
Caudal portion of body short, 
With respiratory trees 
(Molpadiidz) Tentacles digitate (Fig. 11) ; 
calcareous ring with pos- 
terior prolongations. 
brown ellipses, or both . . . Trochostoma 
Caudal portion of body long, 
tapering (Fig. 2); calcareous 
deposits, perforated disks or 
tables with a narrow spire . . Caudina 
NORTH-AMERICAN INVERTEBRATES. 
No. 414.] 
