GLOSSARY. 341 



OO-TOP'O-DA (Gr. octo, eight ; pous, foot). The tribe of Cuttle-fishes with 



eight arms attached to the head. 

 O-DON-TO-CE'TI (Gr. odous, tooth ; ketos, whale). The "toothed" "Whales, in 



contradistinction to the " whalebone " Whales. 



O-DOX'TOID (Gr. odous ; eidos, form). The " odontoid process " is the centrum 

 or body of the first cervical vertebra (atlas}. It is detached from the atlas, 

 and is usually anchylosed with the second cervical vertebra (axis}, and it 

 forms the pivot upon which the head rotates. 



O-DON'TO-PHORE (Gr. odous, tooth ; phero, I carry). The so-called " tongue " 

 or masticatory apparatus of Gasteropoda, Pteropoda, and Cephalopoda. 



(E-SOPH'A-GUS. The gullet or tube leading from the mouth to the stomach. 



OL-I-GO-CH^'TA (Gr. oligoi, few ; chaite, hair). An order of Annelida, com- 

 prising the Earth-worms, in which there are few bristles. 



O-MA'SUM (Lat. for bullock's tripe). The third stomach of Euminants, com- 

 monly called the psalterium, or many-plies. 



OM-NIV O-ROUS (Lat. omnia, everything; voro, I devour). Feeding indis- 

 criminately upon all sorts of food. 



O-PER-CU-LA'TA (Lat. operculum, a lid). A division of pulmonate Gasterop- 

 oda, in which the shell is closed by an operculum. 



O-PER'CU-LTJM. A horny or shelly plate developed in certain Mollusca upon 

 the hinder part of the foot, and serving to close the aperture of the shell 

 when the animal is retracted within it ; also the lid of the shell of a Bala.- 

 n us or Acorn-shell; also the chain of flat bones which cover the gills in 

 many fishes. 



O-PHID'I-A (Gr. ophidion, a little snake). The order of Reptiles comprising 

 the Snakes. 



OPH-I-DO-BA-TBA'CHI-A (Gr. ophis, a snake; batrachos, a frog). Sometimes ap- 

 plied to the order of Snake-like Amphibians comprising the Ccecilice. 



OPH-I-O-MOB'PHA (Gr. ophis; morphe, shape). The order of Amphibia com- 

 prising the Ccecilice. 



OPH-I-U-ROID'E-A (Gr. ophis, a snake; oura, tail: eidos, form). An order of 

 Echinodermata comprising the Brittle-stars and Sand-stars. 



O-PIS-THO-BRANCH-I-A'TA (Gr. opisthen, behind ; bragchia, gills). A division 

 of Gasteropoda in which the gills are placed on the posterior part of the 

 body. 



O-PIS-THO-CCE'LOTIS (Gr. opisthen, behind; Icoilos, hollow). Applied to verte- 

 brae, the bodies of which are hollow or concave behind. 



ORAL (Lat. os. mouth). Connected with the mouth. 



OR-NT-THO-DEL PHI-A (Gr. ornis, a bird ; delphus, womb). The primary divis- 

 ion of Mammals comprising the Monotremata. 



OR-THOP'TE-RA (Gr. orthos, straight ; pteron, wing). An order of Insects. 



OS'CU-LA (Lat. diminutive of os, mouth). 1. The large apertures by which a 

 sponge is perforated (" exhalant apertures"). 2. The suckers with which 

 the Tceniada (Tape-worms and Cystic Worms) are provided. 



OS-SIO'U-LA (Lat. diminutive of os, bone). Literally, small bones. Often used 

 to designate any hard 'structures of small size, such as the calcareous plates 

 in the integument of the Star-fishes. 



OS-TRA-CO'DA (Gr. ostrakon, a shell ; and eidos, form). An order of small 

 Crustaceans which are enclosed in bivalve shells. 



OT'O-LITHS (Gr. ous, ear ; and lithos, stone). The calcareous bodies connected 

 with the sense of hearing, even in its most rudimentary form. 



O-VA'RI-AN VES-I-CLES or CAP'SULES. The generative buds of the Sertularida. 



O'VA-RY (O-VA'RI-UM). The organ by which ova are produced. 



O-VIP'A-ROUS (Lat. ovum, an egg ; and pario, I bring forth). Applied to ani- 

 mals which bring forth eggs, in contradistinction to those which bring forth 

 their young alive. 



O-VI-POS'I-TOR (Lat. ovum; andpono, I place). The organ possessed by 

 some insects, by means of which the eggs are placed in a position suitable 

 for their development. 



O'vi-SAO. The external bag or sac in which certain of the Invertebrates 

 carry their eggs after they are extruded from the body. 



