No. 415.]| MWORTH-AMERICAN INVERTEBRATES. 577 
Key to the Genera. 
CODONID&. 
A. With two or four marginal tentacles, equally developed. 
1. Tentacles and manubrium long and slender, the latter extending 
much beyond the velum; bell hemispherical . . .». Coryne 
2. Tentacles rather short, stout, and capitate; manubrium extending 
but slightly beyond velum; bell conical . . . . . Dipurena 
3. Tentacles rather stout and closely coiled, bell elongate hemispherical 
and with eight rows of nematocysts . . . . . . Ectopleura 
4. Tentacles only two at liberation, four in maturity . . Hydricthys 
5. Tentacles very rudimentary, bell oblong . . . . . . Pennaria 
6. Bell hemispherical, with slight conical apical projection, tentacles 
two, often coiled within bell when disturbed . . . Perigonimus 
B. With a single conspicuous tentacle, others unequally developed or 
rudimentary. 
1. Large tentacle stout and triangular, other three rudimentary ; manu- 
brmumyshortiand thick .{ 9. “<>: ne eit Spy Sa. 
2. A single large and long tentacle, two very small, and one rudi- 
mentary ; bell hemispherical and slightly asymmetrical 
Corymorpha 
3. Bell evidently asymmetrical; a single very large tentacle with 
enlarged base, from which bud proliferously secondary meduse, 
other tentacles very rudimentary . . . . . . . Hybocodon 
TIARID&. 
A. Marginal tentacles two, opposite. 
1. Bell with rather pointed apical projection . . . . . Stomotoca 
B. Marginal tentaeles numerous. 
1. Bell with large, globular, apical process. . . . . . . Turris 
2. Bell without globular apical process . . . . . . Turritopsis 
MARGELID&. 
1. Marginal tentacles eight, symmetrically distributed Pysmew bess 
Podocoryne 
2. Marginal tentacles eight, rudimentary . .. . . . Stylactis 
Tentackesrm e1etelusters wh, a leh) ae. & 02y 4.2.  Ligzia 
Tentacles in four clusters . . . . . . Bougainvillia 
aeta. Gs 
Tentacles in four clusters, each an an erect élavate pair 
Nemopsis 
