GLOSSARY. 489 



Gephtrea (Gr. gejohura, a bridge). A class of tlie Anartliropoda, comprising 



the Spoon-worms {Sipunculus) and their allies. 

 Gizzard. A muscular division of the stomach in Birds, Insects, &c. 

 Gladius (Lat. a sword). Applied to the horny endoskeleton or "pen" of 



certain Cuttle-fishes. 

 Glenoid (Gr. glene, a cavity ; eidos, form). A shallow cavity ; applied espe- 

 cially to the shallow articular cavity in the shoulder-blade to which the 



head of the humerus is jointed. ' 

 Grallatores (Lat. grallce, stilts). The order of the long-legged Wading 



Birds. 

 Graptolitid^ (Gr. grcqilio, I write ; lithos, stone). An extinct sub-class of 



the Hydrozoa. 

 Gregarinida (Lat. gregarius, occurring in numbers together). A class of the 



Protozoa. 

 Guard. Tlie cylindrical fibrous sheath with which the internal chambered 



shell (phragmacone) of a Belemnite is protected. 

 Gymnol^mata (Gr. gumnos, naked; laimos, the throat). An order of the 



Polyzoa in which the mouth is devoid of the valvular structure known as 



the " epistome." 

 Gymnophiona (Gr. gumnos, naked; opli'is, a snake). The order of the ^m- 



phibia comprising the snake-like Ccecilice. 

 Gymnophthalmata (Gr. gumnos; and ophthalmos, the eye). Applied by 



Edward Forbes to those 3Iedusce in which the eye-specks at the margin of 



the disc are unprotected. The division is now abandoned. 

 Gymnosomata (Gr. gumnos; and soma, the body). The order of i^cropocZa 



in which the body is not protected by a shell. 



Hallux (Lat. allcx, the thumb or great toe). The innermost of the five 



digits which normallj^ compose the hind foot of a Vertebrate animal. In 



man, the great toe. 

 Hemiptera (Gr. hemi, half; and ^^^roM, wing). An order of Insects in which 



the anterior wings are sometimes "hemelytra. " 

 Hermaphrodite (Gr. Hermes, Mercury ; Aphrodite, Venus). Possessing the 



organs of both sexes combined. 

 Heterocercal (Gr. heteros, diverse ; kerkos, tail). Applied to the tail of 



Fishes when it is unsymmetrical, or composed of two unequal lobes. 

 Heteropoda (Gr. heteros, diverse ; pedes, feet). An aberrant group of the 



Gasteropods, in which the foot is modified so as to form a swimming organ. 

 Hirudinea (Lat. hirudo, a horse-leech). The order of Annelida comprising 



the Leeches. 

 Histology (Gr. histos, a web ; logos, a discourse). The studj^ of the tissues, 



more especially of the minuter elements of the body. 

 Holocephali (Gr. holos, whole ; Tcephale, head). A sub-order of the Elasmo- 



hranchii comprising the Chimcerce. 

 HoLOSTOMATA (Gr. holos, whole ; stoma, mouth). A division of Gasteropodous 



Molluscs, in which the aperture of the shell is rounded, or " entire." 

 HoLOTHUROiDEA (Gr. holothourion ; and eidos, form). An order of Echinoder- 



mata comprising the Trepangs. 

 HoMOCERCAL (Gr. homos, same ; TcerTcos, tail). Applied to the tail of Fishes 



when it is sjTnmetrical, or composed of two equal lobes. 



