APPENDIX E. 

 GLOSSARY AND GENERAL INDEX. 



Abactinal — in echinoids referring to the 

 dorsal (upper) side of the test. 



Abdomen — in Crustacea, the posterior 

 of the two or three divisions of the 

 body (see Fig. 1542) ; the pygidium. 



Aberrant — differing from the type. 



Abyssal — referring to the great depths 

 of seas or lakes where light is absent. 

 Those animals are abyssal which live 

 at the bottom of abyssal bodies of 

 water. 



Acadian — term for the middle Cambric. 



Acanthopore — in Paleozoic bryozoa, 

 one of the small tubular spines often 

 found at the junction of the zoecia. 

 Function probably similar to that of 

 avicularia. 



Acetabula — in Dibranchiate cephalo- 

 pods, the suckers on the inner side of 

 the arms. 



Acme — the top or highest point. 



Actinal — in echinoids referring to the 

 under or mouth side of the test. 



Actiniform — having a radiate form. 



Adductor — one of the muscles in bi- 

 valve shells used in closing the shell. 

 (In brachiopods, see I., 174, also Fig. 

 392a. In pelecypods, see I., 362, and 

 Fig. 476.) 



Adolescent — youthful (see also on- 

 togeny). 



Adventitious — additional. 



Agglutinate — to unite firmly, as though 

 with glue. 



Agoniatite limestone — in Marcellus di- 

 vision of the middle Devonic of New 

 York, etc. 



Air-chambers — chambers below the liv- 

 ing-chamber in the shells of cepha- 

 lopods. 



Akron dolomite — upper Siluric, west- 

 ern New York. 



Ala (plural alee) — a wing-like process. 



Alar — pertaining to wings. 



Alar septa — the lateral primary septa 

 of the Tetracoralla (see I., 48, and 

 Fig. 75). 



Alate — having wing-like expansions. 



Alimentary canal — the digestive tract 

 or canal of an animal. 



Alivincular — in pelecypods, referring to 

 the ligament when consisting of a 

 single elastic strand stretched from 

 beak to beak, as in Lima. 



Alleghany — middle Coal Measures of 

 Pennsylvania, Ohio, etc. 



Altamaha grit — middle Oligocenic of 

 Georgia. 



Alum Bluff — upper Oligocenic, Gulf 

 coast. 



Alveolus — a cavity. In Belemnoidea 

 the alveolus or alveolar cavity at the 

 broad or anterior end of the guard 

 lodges the phragmocone. 



Ambitus — the greatest circumference. 



Ambulacral — pertaining to the ambu- 

 lacra (see ambulacrum). 

 Ambulacral areas — perforated areas 

 in the test of an echinoderm, 

 through which distensible tube- 

 feet or tentacles project (see Figs. 

 1921, 1928). 

 Ambulacral plates — the plates within 

 the ambulacra. 



Ambulacrum — in echinoderms, the area 

 bounded on each side by one or more 

 rows of holes (for tube-feet or tenta- 

 cles), passing from the ocular plate 

 to the edge of the mouth opening. 

 There are five ambulacra in the test 

 of an echinoderm. 



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