GLOSSARY. 143 



term, " Protista," is applied by Hackel so as to include Protozoa and Proto- 



phyta. 

 PSEUDOPODIA (<|/u8rjs, false ; irovs, foot), the prolongations of the body thrust out 



and drawn in at will, which answer the purpose of limbs in Rhizopoda. 

 PTERODACTYLA (irrep6>>, wing; Sctart/Aoy, finger), an order of extinct reptiles, 



characterised by the fifth digit of the anterior extremity being prolonged so 



as to support a patagium. 

 PTEROPODA (jrrepov, TTOVS, foot), a class of Mollusca in which the Epipodia of the 



foot are developed so as to form wing-like processes by which it swims. 

 PTERYGOID (irrepv, wing ; eTSos, likeness), a bone of the vertebrate skull corre- 

 sponding with the internal pterygoid processes in Man. 

 PULMOGASTEROPODA (pulmo, lung ; yourr-ftp, belly; irovs, foot), those Mollusca 



which walk on their bellies and breathe by lungs. 

 PUPA (a doll), applied to the second, usually motionless, stage of metamorphosis 



in Insects, otherwise called " Nymph " and Chrysalis. 

 PYCNOGONIDA or Pycnogonata (iru/cj/Js, thick ; y6w, knee, ; an order of Arachnida 



with thick jointed legs. 

 PYLORUS (irv\tap6s, a gatekeeper), applied to the valve between the stomach and 



intestines. 

 PYRIFORM (pyrum or pirum, a pear; forma, shape), applied to any tapering 



organ. 

 QUADRATUM (sc. os), four-cornered, square ; the bone by which the mandible 



articulates with the skull in Sauropsida. It probably answers to the Malleus 



in Mammalia. 

 EADIATA (radius, a spoke or ray), applied by Cuvier to a sub-kingdom now broken 



up. The Polypi are divided between Polyzoa and Ccdenterata, which last 



group takes also the Acalephse ; the Entozoa become Scolecida, the Ecliino- 



dermata, Annuloida, and only the Infusoria remain, minus the Sotifera. 

 EADIOLARIA (radiolus, dim. of radius), a class of Protozoa, of which the Sea-egg 



(Sphaerozoon ovo-di-mare) is an example. 

 RADIUS (a spoke), the prcexial bone of the fore-arm which articulates in a line 



with the pollex. 



RAMUS (a branch), applied specially to each half of the mandible in Mammalia. 

 RATIT.S; (ratis, a raft), an order of Birds (Brevipennes of Cuvier, Cursores of 



Illiger), so called because, other birds having a "keeled' sternum, their 



keelless one is like a punt or raft. 

 RmzocEpHALrs (pifr, a root ; Ke4>aA^, a head), a genus of Crustacea which when 



adult bury their hfads in the bodies on which they are parasitic. 

 RHIZODONT (pifr, oSous, a tooth), the attachment of teeth whose fangs branch out, 



and so become ankylosed with the jaw-bone. 

 RHIZOPODA (pifr, itovi. foot), a class of Protozoa in which pseudopodia come out 



of the body like roots. 



RODENTIA (rodere, to gnaw), an order of Mammals, the Glires of Linnaeus. 

 ROSTRUM (a beak), the anterior termination of the carapace in Crustacea. 

 ROTIFERA (rota, a wheel ; fero, bear), or Rotatoria, a class of animalcules separated 

 from the Infusoria, and provided with ciliated fringes round the mouth 

 which when in motion look like two toothed wheels. 



SACRUM (sc. os), the vertebrae which articulate with the ilia to form the pelvis. 

 SAGITTA (an arrow), a genus resembling some Annelida, but with peculiarities 



which have led to its being made into a separate class, " Chsetognatha." 

 SAHCODE (ffdp, flesh ; 686s, way), a name applied to the imperfectly differentiated 



