GLOSSARY. 123 



Rhi'zome (Gr. rhlza, a root ; omos, the same as). An under- 

 ground stem, as that of ferns. 

 Rhizo'poda (Gr. rhlza, a root; pous, podos, a foot). A group 



of the Protozoa having the power of thrusting out root-like 



pseudopodia. 

 Rhizosto'midae (Gr. rhlza, a root; stoma, an opening). A 



family of the Discophora having on their arms a number 



of small openings through which food is taken. 

 Rhom'boid ligament (Gr. rhombos, an equilateral four-sided 



figure with oblique angles ; eidos, shape). A ligament 



attached to the cartilage of the first rib, and to the under 



surface of the clavicle. 

 Rhomboi'deus ma'jor (Gr. rhombos, a rhomb; eidos, form; 



L. major, greater). A muscle passing from the anterior 



dorsal part of the vertebral column to the scapula. 

 Rhomboi'deus mi'nor (Gr. rhombos, a rhomb ; eidos, shape ; 



L. minor, less, smaller). A muscle passing from the 



posterior cervical and anterior dorsal regions of the ver- 

 tebral column to the scapula. 

 Rhynchoce'phala (Gr. rhunchos, a snout ; kephale, the head). 



A group of the Lacertilia containing only the genus 



Sphenodon or Rhynchocephalus. 

 Rhynchonel'lidae (Gr. diminutive of rhunchos, a snout). A 



family of the Brachiopoda. 

 Rhyth'mical (Gr. rhuthmos, measured time). Acting at regular 



intervals, as the pulsation of the heart 

 Ri'gor mor'tis (L. rigidity of death). The stiffening of the 



muscles which takes place shortly after death. 

 Ri'ma glot'tidis (L. cleft of the glottis). The aperture of the 



glottis. 

 Riso'rius muscle (L. rideo, I laugh). One of the muscles of 



the cheek. 

 Roden'tia (L. rodo, I gnaw). A division of the Mammalia 



which embraces the rodents or gnawing animals. 

 Rose'tte (Fr. a small rose, rosette). A plate occupying the 



space between the first five radials in the Crinoidea. 

 Ros'truin (L. the snout of an animal or beak of a bird). 



Applied to the frontal spine of the Crustacea ; also to the 



guard of the Belemnites. 

 Ros'trum of cor'pus callo'sum (L. rostrum, the beak of a bird). 



The inferior reflected portion of the corpus callosum. 

 Ros'trum of sphe'noid bone (L. rostrum, the beak of a bird). 



A sharp prominence of the anterior surface of the sphenoid 



bone of the skull. 



