Structures of two Lycopodium alkaloids, serratinidine (I) from Lycopodium serratum THUNB. var. serratum f. serratum and fawcettidine (XIX) from Lycopodium fawcettii LYLOYD et UNDERWOOD, were examined. In the previous papers, the authors suggested the biogenesis of serratinine and in connection of this, the skeletal structure ((B) in Chart 1) for serratinidine was selected as a working hypothesis. The validity of this assumption was shown by chemical correlation of serratinine ((C), R=OH, in Chart 1) of established structure with serratinidine through the route shown in Chart 2. On the other hand, fawcettidine was first isolated by Burnell from a Jamaican Lycopodium plant but since then there has been no report on the structure. From physical and spectral properties of this alkaloid appeared in the literature, the authors postulated the same skeletal structure for fawcettidine as that of serratinidine. Then, this assumption was proved by chemical conversion of serratinine into fawcettidine along the schemes shown in Chart 5. The present study reveals a new structural type of Lycopodium alkaloid.