GLOSSARY. 



15 



roof, of which their interior margin 

 forms the ridge. 



Dehiscence. The splitting open of the 

 hag containing the insect's eggs. 



Dehiscent. When the base-covers diverge 

 a little at the apex. 



Deltoid. Triangular. 



Dendritic. Branched like a tree. 



Dentarj). Relating to dentition,' or to the 

 teeth ; as, the dentary system. 



Dentate ; Deviated. Toothed ; having 

 tooth-like processes. 



Denticle. A small tooth or projecting 

 point, like the tooth of a fine saw. 



Denticulated Set with small teeth. 



Dentoid. Having the form of teeth. 



Denuded. Divested of covering ; laid 

 bare. 



Depressed. Pressed down or flatted hori- 

 zontally ; low, shallow, flat. 



Deplumed. Stripped of feathers or 

 plumes. 



Dermal. Belonging to the skin. 



Desiccative. Having a tendency to ex- 

 haust moisture. 



Detersive. Having power to cleanse 

 from offensive matter. 



Dextral. Right-handed. Spiral shells 

 are said to be dextral when the aper- 

 ture faces the right hand of the observ- 

 er, the shell being held with the apex 

 upwards. 



Diameter. The thickness of a body, 

 known by a right line passing through 

 its centre. 



Diaphanous. Clear and transparent. 



Diaphragm. A muscular membrane 

 placed transversely across the trunk 

 of the human body, at about its middle 

 portion, dividing it into two pretty 

 nearly equal portions : it is one of the 

 chief organs of respiration, its chief 

 function consisting in alternately in- 

 creasing and diminishing the capacity 

 of the thorax and abdomen. This 

 term is also applied to the septa, by 

 which the chambers of multilocular 

 and other shells are divided from each 

 other. 



Dicerous. A term for any insect that has 

 two antennae. 



Dichotomous. Dividing regularly in 

 pairs. 



Didactylous. Having two toes. 



Didymous. When areolets are nearly 

 divided into two by a nervure. 



Diffused. Dispersed, or extended in all 

 directions. 



Digitated. Branched out into long points, 

 or having finger-shaped processes. 



Digitigrade. Walking on the tips of the 

 toes. 



Dilatability. The quality of admitting 

 expansion by the elastic force of the 

 body itself, or of another elastic sub- 

 stance acting upon it. 



Dilatate. Disproportionably broad in 

 part. 



Dilatation. A spreading or extending in 

 all directions. 



Diluvial. Effected or produced by a 

 deluge, more especially applied to the 

 general deluge in the days of Noah.. 



Diluvium. A deposit of superficial loam, 

 sand, gravel, &c., caused by the del- 

 uge. 



Dimerous. When the trunk of an insect 

 consists of two greater segments. 



Dimidiate. When the base-covers are 

 about half the length of the abdomen. 



Dimidiated. Divided into two equal 

 parts. 



Dimyary. A bivalve whose shell is 

 closed by two muscles. 



Dioptric; Dioptrical. Relating to that 

 part of optics which treats of the re- 

 fraction of light passing through dif- 

 ferent mediums, as through air, water, 

 or glass. 



Dipterous. Having two wings only 

 Pertaining to the Diptera, or those in- 

 sects which have two wings. 



Disc. The middle of a surface. The 

 middle part of the valves of a shell, or 

 that which lies between the umbo and 

 the margin. 



Discoid ; Discoidal. Disc-shaped ; much 

 flattened. A spiral shell is said to be 

 discoidal, when the whorls are so hori- 

 zontally convolute as to form a flat- 

 tened spire. 



Discolorate. Of a different color from 

 the other part. When the upper and 

 under sides of Lepidoptera are of a 

 different color. 



Discontinuous. Where parts which are 

 usually connected are suddenly inter- 

 rupted. 



