Sentence:  "[...] I'm a reg'lar <WSD>Dodman</WSD>, I am," said Mr. Peggotty, by which he meant snail, and this was his allusion to being slow to go, for he had attempted to go after every sentence, and had somehow or other come back again; "but I wish you both well, and I wish you happy!" 
Meaning of the word marked with <WSD> tags:  A land-based snail.