This nemertean, perhaps Baseodiscus sp, was over 4 m long !
Art

Very nice! Baseodiscus mexicanus.
Known from Baja to Galapagos.
Can I use this pic too? 
Can you give me some locality, habitat and depth information?
Thanks,
--Jon
color pattern looks a bit different from B. mexicanus in Kerstitch, but if you say it is B. mexicanus, then it must be one ! 
of course, you can use it !
hey, here is the length of the worm, measured in our lab, my assistant is for scale
Art

forgot the details:
extreme low tide, rocky shore, under rock, off Casco Viejo, Panamá
here a close-up of the head
Art
