GLOSSARY. 



821 



Ambulatory — walking. 



Ames limestone — Conemaugh forma- 

 tion, upper Coal Measures of Penn- 

 sylvania, Ohio, etc. 



Amherstburg dolomite — upper Mon- 

 roan of Michigan, Ohio, etc. 



Ammoniticone — a closely-coiled Ammo- 

 noid shell (see II., 19). 



Amphidetic — in pelecypods, referring to 

 the ligament when extended on both 

 sides of the beak, as in Glycimeris. 



Anal — pertaining to the anus. For use 

 in crinoids, see II., 491, and Fig. 

 1858. 



Anal opening — see anus. 

 Anal tube — in Fistulate crinoids, the 

 special tube for carrying off the 

 waste (see Figs. 1865, 1871). 

 Anal vein — in insects one of the wing 

 veins (see Fig. 1724)- 



Anaptychus — in many Ammonoid ceph- 

 alopods the single calcareous oper- 

 culum. 



Anastomose — to intercommunicate by 

 branching, usually producing a net- 

 like appearance. 



Anchylose — to unite solidly ; to grow 

 together into one. 



Anderdon limestone — upper Monroan of 

 Michigan, Ohio, etc. 



Angulated — with angles or corners. 



Anisic — middle Triassic. 



Annular — ring-shaped. 



Annulations — rings or ring-like seg- 

 ments. 



Annulus — a ring ; in trilobites, a seg- 

 ment of the thorax. 



Anodont dentition — in pelecypods, with 

 no teeth, as in Anodonta. 



Antenna — a movable, jointed organ of 

 sensation attached to the heads of 

 insects and crustaceans (see Fig. 

 1692). 



Antennules — in Crustacea, the anterior 

 of the two pairs of antennae when 

 two are present (see Fig. 1692). 



Antepenult — the third from the last, 

 the one before the penult. 



Anterior — front. In brachiopods, the 

 side opposite the beak. In pelecy- 



pods, the end opposite the pallial 

 sinus. In gastropods, the end with 

 the aperture. 



Anticosti group — lower and middle( ?) 

 Siluric of Atlantic coast. 



Antietam sandstone — lower Cambric, 

 Pennsylvania-Maryland. 



Antisiphonal lobe — in cephalopod shells 

 the lobe on the dorsum, opposite the 

 siphuncle. 



Antrim shale — upper Devonic, Michi- 

 gan. 



Anus — the posterior opening of the ali- 

 mentary canal, through which the 

 waste matter is thrown out of the 

 body. 



Aperture — the opening of shells, cells, 

 etc. 



Apex — the tip or top of anything. In 

 gastropod shells, the terminal or first 

 formed portion. 



Apical — pertaining to the apex or sum- 

 mit. 



Apical angle — the angle included by 



the two sides of the spire of a shell. 



Apical system — in echinoids, the set 



of ten plates at the summit of the 



test (see II., 574, Fig. i93Sa). 



Apison shale — lower Cambric, southern 

 Appalachians. 



Apophysis — a marked prominence in 

 animals or plants due to natural 

 growth ; a calcareous process in the 

 interior of shells, etc. 



Appressed — pressed closely against. 



Aptychus — in many Ammonoid cepha- 

 lopods, the double calcareous opercu- 

 lum closing the opening of the shell 

 when the soft parts of the animal are 

 withdrawn. 



Aquia — lower Eocenic of the Atlantic 

 coast. 



Aragonite — calcium carbonate (CaCOs) 

 crystallizing in the orthorhombic sys- 

 tem. In shells it is chalky and opaque. 



Arborescent — branching like a tree. 



Arbuckle limestone — middle Cambric to 

 lower Ordovicic, Oklahoma. 



Arcuate — arched ; bent like a bow. 



