This manuscript is entitled “Les premieres Euvres de Jacques Devaulx, pillote en la marine” and is dated 1583 . It is a treatise on how to navigate the globe and shows the insights and practical knowledge at that time. I also found a nice pictures showing the Americas, so here are blending my two worlds.
On f. 18r two decorated initials can be seen, one of which with a bird and one (letter ‘A’) with a stylised dextral snail. Where the animal comes out of the aperture, two protuberances are seen; they seem odd at least.
On folio 21r, the lower initial (letter ‘L’) is decorated with a hybrid devil pointing a lance (?) in the direction of the stylised, dextral snail with two tentacles and an eye-spot; again, at the aperture, two protuberances may be seen, which seem misplaced.
Despite the marine subject, the decorations are terrestrial and are reminiscences from earlier, religious manuscripts.
 BNF, Ms. Français 150, 31 ff. http://gallica.bnf.fr/ark:/12148/btv1b550024840 (permalink).