GLOSSARY 



abdomen, in Arthropoda, the hinder- 

 most of the three divisions of the 

 body, 59. 



aboral, the side of the body opposite 

 to the mouth, 193. 



alveolus, a depression, e.g. the socket 

 of a tooth, 280. 



angulated, forming an angle or sharp 

 corner ; opposed to rounded, 249. 



antenna, horn or feeler, one of the 

 anterior tactile appendages of Ar- 

 thropoda and Mollusca, 4, 4(3. 



anterior, situated at the front end of 

 the body. 



anus, the posterior opening of the food 

 canal. 



aorta, the main blood-vessel coming 

 from the heart. 



articular, relating to a joint; the 

 hinge bone of the lower jaw of 

 fishes, 232. 



atripore, the external opening of the 

 atrium, 249. 



atrium, or vestibule, a chamber placed 

 either in front of the mouth or, in 

 Chordata, around the gill-slits. 



auditory clubs, club-shaped sense or- 

 gans on the margin of the bell of 

 jelly-fishes, 221. 



basihyal, a bone found in fishes, form- 

 ing the base of the U-shaped arch 

 which supports the tongue, 232. 



bifid, two-parted. 



bivalve, having two valves or shells, 

 131, 178. 



blastula, a stage in the early develop- 

 ment of the egg when it forms a 

 hollow sphere, 193. 



branchial, relating to the gills. 



branchiate, bearing gills, 131. 



branchiostegal rays, the bony rays 

 supporting the membrane below the 

 bones of the operculum in fishes, 

 232. 



buccal, pertaining to the mouth cavity 

 or cheeks, 59, 143. 



byssus, a tuft of tough threads spun 

 from the foot of bivalves and used 

 for attachment to foreign bodies, 

 180. 



calcareous, consisting of a calcium or 

 lime compound. 



calcified, rendered calcareous by depo- 

 sition of salts of lime. 



callus, a soft substance secreted over 

 a harder bony material, 175. 



calyx, cup. 



cambered, concave on the under side, 

 42. 



canine, or canine tooth, the pointed 

 tooth situated immediately behind 

 the front cutting teeth, 331. 



capsule, a little sac containing a fluid. 



carapace, the thick shell or skin cov- 

 ering the back of Crustacea or Che- 

 Ionia, 103, 280. 



cardinal, belonging to the hinge, as 

 the teeth of lamellibranch shells, 

 188. 



carnivorous, flesh-eating. 



391 



