GLOSSARY. 171 



Sclerodermic (Gr. scleros, hard ; derma, skin) Applied to the 

 coral which is formed within the tissues of the reef-building 

 polypes. 



Scolecida (Gr. slcolex, a worm) A class of Annuloida, including 

 the tape-Worm and other internal parasites. 



Septa (Lat. partitions) Applied to the walls of the chambers in 

 the nautilus, &c. 



Sertularida (Lat. sertitm, a wreath) A group of Hydrozoa. 



Sessile (Lat. sedeo, I sit) Not supported upon stalks; the op- 

 posite of pedunculated. 



Siliceous (Lat. silex, flint) Composed of silex or flint. 



Siphon (Gr. a tube) One of the breathing tubes in the Mollusca. 



Siphuncle (Lat. siphunculus, a little tube) The tube which con- 

 nects the chambers of the shells in some of the Cephalopoda. 



Somatic (Gr. soma, the body) Belonging to the body. 



Somite (Gr. soma) A segment of the body in the Annulosa. 



Spermatozoa (Gr. sperma, seed; zoon, an animal) Minute or- 

 ganisms found in the sperm cells of animals. 



Spicula (Lat. spiculum, a point) Applied to the needle-shaped, 

 siliceous bodies found in sponges, c. 



Spinnerets The teat-like organs situated at the extremity of the 

 abdomen in spiders, &c., through which the threads that 

 form the webs are drawn. 



Spongida A group of Rhizopoda, including the sponges. 

 I Sternum The breast-bone. 



Stigmata (Gr. stigma, a mark) The apertures by which the 

 tracheae of insects, &c., communicate with the atmosphere. 



Swimmerets Limbs attached to the abdomen in the Crustacea 

 which are used in swimming. 



Tseniada (Gr. tainia, a ribbon) The group of Scolecida to which 



the tape-worms belong, 

 i. Tarso-metatarsus A bone in the leg of a bird formed by the 



amalgamation of the lower portion of the tarsus with the 



metatarsus. 



Tarsus The small bones which form the ankle. 

 Telson (Gr. the end) The somite at the extremity of the abdomen 



in the Crustacea. 

 Test (Lat. testa, a shell) Applied to the calcareous covering of 



the sea-urchins, &c. 

 Tetrabranchiata (Gr. tetras, four; branchiae, gills) An order of 



Cephalopoda to which the pearly nautilus belongs. They 



possess four gills. 

 Thalassa-collida (Gr. thalassa, the sea; kolla, glue) A group of 



Protozoa. 



Theca (Gr. theke)A sheath or case. 

 Thorax (Gr. a breastplate) The chest. 



