An extract from Morris, L., 1748. Plans of Harbours, Bars, Bays and Roads in St. George's Channel. The extract (page 47) provides the then distinction between bottle-nosed dolphins and harbour porpoise.
The extract reads as follows: “As Naturalists have not made a Distinction between Bottle-noses and Porpesses, it may not be improper to give the following Account of the Difference between them.
The Snout of the Porpess is sharp, and comes to a Point like a Cone; the Snout of the Bottle-nose is blunt, and they also grow to a larger Size than the Porpess, and have more Blubber upon them, and each Kind go in Shoals by themselves.
It is generally observed, that when the Porpesses play, there is one much larger than the rest among them, as if he as their King or Leader.
The Natives here call them in general Llambidyddion (q.d. Tumblers) and Pysgod duon, (Black Fish) but they are seen of various Colours; whitish, speckled, and black: and Fishermen say, the older and larger they grow, the blacker they are.
There might be great Profit made of these Fish, if there was a proper Method of taking them.”