| Observations in Ceylon | Haeckel | Loris | 1972 | XII | 6 | 316 - 318 | General |
| Observations of a Scops Owl | Dissanayake | Loris | 1976 | XIV | 2 | 97 - 98 | General |
| Observations on a Nesting Grebe | de Zylva | Loris | 1968 | XI | 4 | 210 - 213 | General |
| Observations on Computations of the Mortality Rate Among Immigrant Indian Labourers in Ceylon in the Coffee Period | Roberts | Ceylon Journal of Historial & Social Studies, The | 1966 | 9 | 1 | 81 - 84 | General |
| Observations on Indothele lanka, a Funnel Web Spider from Sri Lanka | Kuntner | Journal of South Asian Natural History | 1997 | 2 | 2 | 199 - 204 | General |
| Observations on the Annual Mass Migration of Brown Winged Terns off the Coast of Colombo | De Silva | Loris | 1982 | XVI | 1 | 27 - 28 | General |
| Observations on the Endemic Banded Mountain Loach | Nalinda | Loris | 1985 | XVII | 2 | 50 - 52 | General |
| Observations on the Endemic Redlip Goby | Nalinda | Loris | 1989 | XVIII | 4 | 150 - 151 | General |
| Observations on the Horned Lizard - Cerataphora Stoddarti | Ilangakoon | Loris | 1990 | XIX | 1 | 44 - 45 | General |
| Observations on the Life History of the Nematode, Panagrolaimus Rigidus | Gadd | Spolia Zeylanica | 1943 | 23 | 2 | 65 - 69 | General |
| Observations on the Nests, Eggs & Larvae of Ophiocephalus Striatus | Willey | Spolia Zeylanica | 1909 | VI | XXIII | 108 - 123 | General |
| Observations on the Philippine Shrike | Gunawardana | Loris | 1991 | XIX | 3 | 95 - 96 | General |
| Observations on the Sambar Cervus Unicolor Kerr 1792 in the Ruhuna National Park | Santiapillai | Ceylon Journal of Science | 1981 | 14 | 1 & 2 | 193 - 205 | General |
| Occurence of Gonostoma Elongata Gunther & Xiphasia Setifer Swainson off Ceylon, The | De Silva | Spolia Zeylanica | 1958 | 28 | 2 | 141 - 144 | General |
| Occurence of Solenostoma off the Coast of Ceylon | Willey | Spolia Zeylanica | 1909 | VI | XXIII | 102 - 107 | General |
| Octopus, The | De Silva | Loris | 1978 | XIV | 6 | 347 - 349 | General |
| Odyssey of an Orchid, An | David | Loris | 1980 | XVIII | 4 | 152 - 153 | General |
| Of Dutch Painters and Predikants..... | De Silva | 400 Years of Sri Lanka-Netherlands Relations | August 2002 | N/A | N/A | 1 - 16 | History |
| Of Elephants & Frogs | Peiris | Loris | 2000 | 22 | 4 | 29 -31 | General |
| Of Pig Holes & Leopards | Norris | Loris | 1967 | XI | 1 | 6 - 11 | General |
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