Sentence:  I ought not to omit to add that this formation in addition to its other peculiarities is characterised by a notable proportion of bitumen, so that a strong <WSD>petroleous</WSD> odor is perceptible immediately on the application of the hydrochloric acid and not less so after the subsidence of the effervescence, 
Meaning of the word marked with <WSD> tags:  Characteristic of oil or petroleum.