GLOSSARY. 395 



WHORL. The spiral turn of a univalve shell. 



XIPHOSURA (Gr. xiphos, a sword ; and oura, tail). An order of Crustacea, 

 comprising the Limuli or King-Crabs, characterised by their long sword- 

 like tails. , 



XYLOBIUS (Gr. xulon, wood; bios, life). An extinct genus of Myriapods, 

 named in allusion to the fact that the animal lived on decaying wood. 



ZAPHRENTIS (proper name). A genus of Rugose Corals. 



ZEUGT.ODONTID.S: (Gr. zeugle, a yoke ; odous, a tooth). An extinct family of 

 Cetaceans, in which the molar teeth are two-fauged, and look as if composed 

 of two parts united by a neck. 



ZOOPHYTE (Gr. zoon, animal ; pkuton, plant). Loosely applied to many plant- 

 like animals, such as Sponges, Corals, Sea-anemones, Sea-mats, &c. 



