376 GLOSSARY. 



Dex'tral (Lat. dextra^ the right hand). Right-handed: applied to the direo- 

 tiou of the spiral in the greater number of univalve sheUe. 



Di'a-phragm (Ur. diapkragnia^ a partition). The "midriff," or the muscle 

 whicli in Mammalia forms a partition between the cavities of the thorax 

 and abdomen. 



Di-a-3te',ua (Gr. dla^ apart; histemi^ to pUice). A gap or interval, especially 

 between teeth. 



Di-as'to-le (Gr. diastdlo^ I separate or expand). The expansion of a contrac- 

 tile cavity sucL as tiie heart, which follows its contraction or " systole." 



Di-a-to-ma'ce-^ (Gr. diatemno, 1 sever). Au order of minute plants, which 

 are provided witli siliceous envelopes. 



Di-brancu-i-a'ta (Gr. dis^ twice; bragchla^ .^ills). The order of Cephalopoda 

 (comprising the Cuttle-tishes, etc.), in which only two gills are present. 



Di-oyn-o-don'ti-a (Gr. dl.^, twice ; kuon^ dog ; odons^ tooth). An extinct order 

 of Reptiles. 



Di-del'phi-a (Gr. dls^ Iw'iQd ; dJphus, ■womb). The subdivision of Mammals 

 comprising the Marsupials. 



Dig'it (Lat. digitus^ a finger). A finger or toe. 



Dig-i-ti-gra'ua (Lat. diijttu^; <jradiof\ 1 walk). A subdivision of llie Oar- 

 nivora. 



Dig'i-ti-grade. Walking upon the tips of the toes, and not upon the soles 

 of the feet. 



DiM-E-KO-so'jiA-TA ( (Tr. d/-'f ; mi'/'Of!, part; .s"0»;cr, body). An orderof -Jrac7/;,/'/a, 

 comprising the true bpiders, so called from the marked division of the body 

 into two regions, the cepbalothorax and al>domen. The name Arauelda is 

 otten employed for tho order. 



Dlm'v-a-kv I (Ir. dis, t"¥F;ce ; mus^ muscle). Applied to those bivalve Molluscs 

 {Lamell ibranchiata) ia which the shell is closed by two adductor muscles. 



Di-tE'ciou8 (Gr. dis^ twice; oikos. house). Having the sexes distinct; applied 

 to species which consist of male and female individuals. 



DipHT-o-DONT (Gr. r7^/,5, twice ; ^Awo, I generate ; odous^ tooth). Applied to 

 those Manmnals which have two sets of teeth. 



DipH-y-o-zo'oiDS. Detached reproductive portions of adult Calyrovhorida;^ an 

 order of oceanic Ilydrozoa. 



Dip'noi (Gr. dis^ twice; pnoe^ breath). The order of Fishes represented by 

 the Lepidosiren. 



Dip'ter-a (Gr. dls^ twice ; ^^t^ro/i, wing). An order of Insects characterized 

 by the possession of two wings. 



Discoid (Gr. diskos, a quoit ; eiaos, form). Shaped like a round plate or quoit. 



Dis-coph'o-ra (Gr. dishos^ a quoit; phero^ I carry). This term is applied to 

 the Medusce^ or Jelly-iishes, from their form ; and is sometimes used to 

 designate the order of the Leeches {Hirudinea)^ from the suctorial discs 

 which these animals possess. 



Dis-SEp'i-MENTs ( Lat. dlsypio, I partition off). Partitions. Used in a restricted 

 sense to designate certain imperfect transverse partitions, which grow from 

 the septa of many corals. 



Dis'tal. Applied to the quickly-growing end of the hvdrosoma of r Ilf/dro- 

 zo'iii • the opposite, or ^'proximal," extremity growing less rapidly, and 

 being the end by which the organism is fixed, when attached at all. 



Di-ur'nal (Lat. dles^ dayj. Applied to animals which are active during :he 

 day. 



Di-vj;r-tic'u-ll'm (Lat. diverticulum^ a by-road). A lateral tube with a blind 

 extremity springing from the side of another tul^e. 



Dor'sal (Lat. dorsum^ back). Connected with the back. 



DoR-si-BKANCii'i-ATE (Lat. dorsum^ the back ; Gr. bragehia^ gills). Having ex- 

 ternal gills attached to the back ; applied to certain Anndidcn and M^dluscs, 

 The term is of mongrel composition, and " noti-ibranchiate " is more cor- 

 rectly employed. 



Eo'de-ron (Gr. ek, out; diro:^^ skin). The outer plane of growth of the ex- 

 ternal integumentary layer (viz., the ectoderm, or epidermis). 



