GLOSSARY. 39 



Di'atom (Gr. diatemno, to separate, cut through). A minute 



vegetable organism provided with a flinty covering. 

 Libranchia'ta (Gr. dis, double ; branchia, a gill). The group 



of Cephalopods which possess two gills. 

 Dicho'tomous (Gr. dichotomia, a division into two parts). 



Twice divided ; doubly forked. 

 Dicotyledonous (Gr. dis, double ; kotyledon, a cup-shaped 



hollow). The group of plants the embryos of which 



have two seed-leaves or cotyledons. 

 Dicro'tic (Gr. dis, double ; kroteo, I beat). Having a double 



beat; applied to the arterial pulse when exhibiting this 



phenomenon. 

 Dicye'mida (Gr. dis, double; kuema, embryo). A group of 



parasitic animals found in the renal organs of Cephalopods, 



and placed provisionally between the Protozoa and the 



Metazoa, under the designation of Mesozoa. The embryo 



exists under two forms. 

 Dicynodon'tia (Gr. dis, double ; kynodous, kynodontos, a dog's 



tooth). A group of extinct reptiles having usually two 



large tusks. 

 Didac'tyle (Gr. dis, double; daktulos, a finger). Having two 



digits. 

 Didel'phla (Gr. dis, double; delphus, the womb). A group of 



mammals, so called because the vagina is double. 

 Dience'phalon (Gr. dia, between ; enkephalon, the brain). The 



posterior division of the anterior primary cerebral vesicle, 



usually termed the Thalamencephalon. 

 Diete'tics (Gr. diaitao, to feed). A term for the consideration 



of a system of regulating the diet, so as best to secure the 



restoration or maintenance of health. 

 Digas'tric (Gr. dis, double; gaster, the belly). Two-bellied ; 



applied generally to muscles which are fleshy at each end, 



and have a tendon in the middle. Specially applied to 



the muscle which depresses the lower jaw. 

 Di'git (L. digit us, the finger or toe). A finger or toe. 

 Digi'tigrade (L. digitus, the finger or toe; gradus, a step). 



Walking on the toes, these being the only parts of the foot 



which touch the ground in digitigrade animals. 

 Dimor'phodon (Gr. dis, double ; morphe, form ; odous, odontos, 



a tooth). A genus of extinct Pterosaurians having the 



posterior teeth very short, the anterior long. 

 Dinorni'thidae (Gr. dinoo, to spin round ; or/it's, ornithos, a bird). 



A subdivision of ratite birds which comprises the moas. 



