The last mystery object I gave you was one of the Dead Zoo’s Blaschka glass models and it proved to be a nice challenge. So here’s another one of them that’s become dissociated from its data in the mists of time for you investigate:
Same rules as last time – let’s see if you can figure out the species and the catalogue number (here’s a link to the catalogue to help with that). Have fun!
Zygoma 
Well… to start it was a SpongeBob’s First appearance: “A Pal for Gary”
I see many horns with four lines.
473
I am agreeing with the Polycera, but not the quadrilineata. These models, made of glass, were very true to the color of the specimen, and there is just not enough vivid yellow for the Polycera quadrilineata. Hummm. I have more checking to do. Can’t find a good photo of the back for quadrilineata.
Possible color morphotype of the P.q?
Yes. Despite the quadrilineata (four lines) name, some morphotypes don’t have stripes:
https://www.researchgate.net/figure/P-quadrilineata-A-F-Yellow-orange-colour-morphotype-G-M-Striped-colour-morphotype_fig3_343321671
473
I’m with Adam Yates – many horns. I have four things not to say about this.
Nudibranch?
How did you keep these things from breaking all those years?
Many have been on display almost continuously, so it’s minimised handling. It does mean they’re quite faded though
These are such amazing models!!
I think it is P. quadrilineata. The Cornell website has several images of this model.