GLOSSARY. 77 



M. 



Macrauche'nidae (Gr. makrauchen, makrauchenos, long-necked). 

 An extinct family of the Perissodactyla. 



Ma'cromere (Gr. makros, long; meros, a part). The larger of 

 the two unequal masses into which the vitellus divides in 

 the development of the Lamellibranchiata, termed by 

 Rabl the "vegetative cell." 



Macru'ra (Gr. makros, long ; our a, tail). A subdivision of the 

 Podophthalmia (Crustacea), in the members of which the 

 abdomen is largely developed. 



Ma'cula germina'tiva (L. germinal spot). The nucleolus of the 

 germinal vesicle of the ovum. 



Ma'cula lu'tea (L. yellow spot). The bright spot on the retina 

 of the eye, which is most sensitive to the action of light. 



Madrepo'ric canals. Tubular prolongations of the circular 

 ambulacral vessel in the Echinodermata. 



Madrepo'ric tu'bercle. A convex porous plate on the aboral 

 face of some Echinoderms. 



Madrepo'riform. A term applied to the madreporic tubercle. 



Madrepo'rite. Another name for the madreporic ttibercle. 



Malacosco'lices (Gr. malakos, soft ; skolex, a worm). A divi- 

 sion of the Invertebrata proposed by Huxley to include 

 the Polyzoa and the Brachiopoda : the name signifies the 

 connexion of these groups, on the one hand with the 

 Mollusca, on the other with the Worms. 



Malacostra'ca (Gr. maldkos, soft). A division of the Crustacea 

 which includes the . Podophthalmia, the Cumacea, the 

 Edriophthalmia, and the Stomatopoda. 



Malacozo'ic series (Gr. maldkos, soft; zoon, an animal). A 

 series of the Invertebrata which includes the Malacoscolices 

 and the Mollusca. 



Malar (L. mala, the prominence of the cheek). The cheek- 

 bone. 



Malle'olar (L. malleolus, a little hammer, the ankle). A bone 

 in the Ruminantia which articulates below with the cal- 

 caneum, and above with the astragalus. Applied also to 

 two small arteries distributed to this region. 



Malle'olus (L. a little hammer). The name given to a process 

 of the tibia and of the fibula. 



Malleus (L. hammer). The small bone of the middle ear 

 which articulates on the one hand with the tympanic 



