Ricordea, [371]

Ridley, [216] n., [352] n.

Riisea, [355]

Ring-canal, of water-vascular system, [428];

of Asterias rubens, [441];

of Echinus esculentus, [517];

of Holothuria nigra, [566]

Robertson, on the habits of Echinocardium cordatum, [552]

Rock-urchins, [529]

Rodents, hosts of Trypanosoma lewisii, [119]