152 GLOSSARY. 



Umbilicus (L. the navel). The point in the middle line of the 



abdomen at which the somatopleures of the foetus unite. 



Also the name given to two apertures (superior and inferior} 



in the calamus of a bird's feather. 

 Um'bo (pi. umbones, L. a boss). The beak of a bivalve shell. 



Also a depression in the integument of the larva of an 



Echinoderm. 

 Un'ciform (L. uncus, a hook; formis, shape). One of the 



bones of the carpus, also termed uncinatum and hamatum. 

 Un'cinate (L. uncus, a hook). Hooked. Applied to a process 



of the ethmoid bone. 

 Un'gual phalan'ges (L. unguis, a nail). The terminal phalanges 



of the digits, so called because provided with nails or claws. 

 Un'gues (L. unguis, a nail). Applied to the pointed claws 



which terminate the legs in the Insecta. 

 Un'guis (L. a nail). The narrow stalk by which the alae of a 



papilionaceous flower are attached to the corolla. 

 Un'gulata (L. ungula, a hoof). A group of the Non-deciduate 



Mammalia. 

 Unguligrade (L. ungula, a hoof; gradus, a step). Applied to 



those animals which walk upon hoofs, which consist of the 



ungual phalanges encased in thick horny sheaths. 

 Unipolar (L. unus, one ; polus, the pole). Having a single 



pole. Applied to those ganglionic nerve cells which have 



but one radiating process. 

 U'nivalve (L.'unus, one; valvce, folding doors). Applied to 



those Mollusca which have shells composed of a single 



piece. 



U'rachus (Gr. ouron, urine ; echo, I hold). One of the liga- 

 ments of the bladder formed by the remaining constricted 



portion of the allantois of the foetus. 

 Ure'a (Gr. ouron, urine). A nitrogenous substance found 



abundantly in the urine, and produced by the waste 01 



nitrogenous material both in the food and in the tissues. 

 Ure'ter (Gr. oureter, the urinary duct). A duct leading from 



the kidney to the urinary bladder. 

 Ure'thra (Gr. ourethrd). The canal leading from the urinary 



bladder to the exterior. 

 Uri'na ci'bi (L. urine of food). The name given to the urine 



passed immediately after food has been taken. 

 Uri'na po'tus (L. urine of drink). The name given to the urine 



passed immediately after a quantity of fluid has been 



drunk. 



