The Collaborative International Dictionary
                    Shell-less
                    
                        
                
                                                                    Shell-less \Shell"-less\, a.
   Having no shell. 
--J. Burroughs.
Wiktionary
                    shell-less
                    
                        
                
                                                                    a. 1 Lacking a shell. 2 Unprotected, vulnerable.
Usage examples of "shell-less".
He waved a stumpy arm toward a group of shell-less Fustians standing by a massive hoist.
In water, shell-less molluscs can grow to large sizes, and include squid and octopus.