Quadrumana

(Lat. quatuor, four; manus, hand). The order of Mammals comprising the Apes, Monkeys, Baboons, Lemurs, etc.

Radiata

(Lat. radius, a ray). Formerly applied to a large number of animals which are now placed in separate sub-kingdoms (e.g., the Coelenterata, the Echinodermata, the Infusoria, &c).

Radiolaria

(Lat. radius, a ray). A division of Protozoa.

Radius

(Lat. a spoke or ray). The innermost of the two bones of the forearm of the higher Vertebrates. It carries the thumb, when present, and corresponds with the tibia of the hind-limb.

Radula

(Lat. radula, a scraping-iron). An epithet often given to the toothed lingual ribbon or " odontophore " of the higher Mollusca.

Ramus

(Lat. a branch). Applied to each half or branch of the lower jaw or mandible of Vertebrates.

Raptores

(Lat. rapto, I plunder). The order of the Birds of Prey.

Rasores

(Lat. rado, I scratch). The order of the Scratching Birds (Fowls, Pigeons, &c).

Ratitae

(Lat. rates, a raft). Applied by Huxley to the Cursorial Birds, which do not fly, and have therefore a raft-like sternum without any median keel.

Rectum

(Lat. rectus, straight). The terminal portion of the intestinal canal, opening at the surface of the body at the anus.

Reptilia

(Lat. repto, I crawl). The class of the Vertebrata comprising the Tortoises, Snakes, Lizards, Crocodiles, etc.

Reticulosa

(Lat. reticulum, a net). Employed by Dr Carpenter to designate those Protozoa, such as the Foraminifera, in which the pseudopodia run into one another and form a network.

Reticulum

(Lat. a net). The second division of the complex stomach of Ruminants, often called the "honeycomb-bag."

Reversed

Applied to spiral univalves, in which the direction of the spiral is the reverse of the normal - i.e., sinistral.

Rhabdophora

(Gr. rhabdos, a rod; and phew, I carry). Employed by Prof. Allman as a name for the Graptolites, in consequence of their commonly possessing a chitinous rod or axis supporting the perisarc.

Rhizophaga

(Gr. rhiza, root; phago, I eat). A group of the Marsupials.

Rhizopoda

(Gr. rhiza, a root; and pous, foot). The division of Protozoa comprising all those which are capable of emitting pseudopodia.

Rhopalocera

(Gr. rhopalon, club; keras, horn). A name given to the Butterflies among the Lepidoptera in allusion to the fact that the antennae are clubbed at the end.

Rhyncholites

(Gr. rhunchos, beak ; and lithos, stone). Beak-shaped fossils, consisting of the mandibles of Cephalopoda.

Rodentia

(Lat. rodo, I gnaw). An order of the Mammals ; often called Glires (Lat. glis, a dormouse).

Rostrum

(Lat. rostrum, beak). The "beak" or suctorial organ formed by the appendages of the mouth in certain insects.