INDEX 



623 



tail spine in, 84. 



Thompsonl, 144. 

 Olenida, Haeckel, 112. 

 Olenidte, 129, 131, 139, 157. 



defined, 141. 



eye-line in, 141. 

 Oleninffi, 145. 

 Olenoldes, 142, 145. 

 Olenus, 129, 139, 142, 143, 145. 



ceplialon of, 129. 



eye-line in, 223. 

 Onchohchas, 150. 



glabella in, 150. 

 Onom'is horrida, 74. 



splnosa, spiny variety of, 74. 

 ontogeny and phylogeuy in Brachiop- 

 oda, correlations of, 286. 



a standard of classification, 1 20. 



early stages in, Hyatt, 95. 



of a spiuose individual, 18. 



of spiniferous species of Mollusca, 

 19. 

 Onycopyge, 153, 155, 156. 

 Opisthocomus cristaius, thumb and index 



finger in, 84. 

 Opisthoparia, 124, 128, 129, 131, 132, 

 139, 140, 141, 151, 152, 153. 



defined, 138. 

 Orhiculoidea, 231, 244, 268. 



development of, 239. 



discoid form of shell in, 287. 



early stages of Paleozoic, 287. 



first appearance of, 287. 



minuta, brachial valve of, 233. 



ontogeny of, 287. 



pedicle-opening in, 241. 



protegulum in, 230, 234. 



nepionic stage in, 267. 



stages of development in, 265, 266. 

 Orhulina imiversa, pelagic forms of, 66. 

 Orchestidie, epimeral and tergal spines 



in, 36. 

 orders, foundation of, Agassiz, 242. 

 Oreaster gigas, spines in, 51. 



occidentalis, spines in, 51. 

 organisms, correlations of volumes and 

 surface of, Ryder, 27. 



parasitic, life history of, 40. 



repetition of parts universal among, 

 Bateson, 67. 

 organs, rudimentary, origin of so-called, 

 Darwin, 80. 



origin, categories of, 26. 

 Ornithopoda, functional digits in, 85. 

 Ornithorhjnchus, spur on hind legs of, 



9, 59. 

 OroRphcBra Huxleyi, spines in, 48. 

 Orthidse, 317. 



deltidial development in, 393. 

 Orthis, 256, 394, 395, 399, 401. 

 acutiloba, 400. 

 biloha, 399. 

 dorsal fissure in, 263. 

 elegantula, 317. 

 group, 231, 245, 399. 

 high hinge-area in, 266. 

 kybrida, 321. 

 pedicle-apertures on valves of, 394. 



-opening in, 241. 

 spiniform processes in, 78. 

 subnodosa, 315. 

 teeth in, 252. 

 Orthisina, 245, 252, 257, 395. 

 pedicle-opening in, 241. 

 Orthothetes, 231, 245. 



absence of straight hinge-line in 



young, 268. 

 cavity of pedicle-sheath in, 395. 

 deltidium of, 386. 

 subplanus, 315. 



aperture of ventral valve in, 



394. 

 concentric ornamentation in, 



397. 

 deltidial plates in, 394, 395. 

 development in, 333. 

 discussion of, 327. 

 hinge in, 333. 

 tenuis, 315. 

 Oryctocephalinae, 145. 

 Oryctocephalus, 142, 143, 145. 

 Ostracoda, 114, 184. 



development of extinct, Verworn, 



310. 

 respiration in, 218. 

 ostra;iform growth in Spondylus, 20, 21. 

 Ostrea, relation to Avicida, 255. 

 smooth prodissoconch of, 18. 

 virginiana, prodissoconch of, 20. 

 Ovibos mosch(Uus, horns in, 53. 

 Owen, R., Artbropomata and Lyopom- 

 ata, 242. 



antlers in deer, 22. 

 ox, development of horns in, 14. 



