From G. R. Waterhouse   [7 March 1855]

be sent tomorrow—

I have lately been studying the head of the Ichthyosaurus¹ — how like it is in all its superficial characters to the Cetacean skull, and yet in essential—or type characters, it is totally different— even the upper jaw of the one, is not the upper jaw of the other— the snout with its teeth in the Ichthyosaurus is made up of the intermaxillaries in the Cetacean it is the maxillaries—&c— I don’t know a grander example of difference of types, (combined with much superficial resemblance), than is offered by the two beasts—

Yours faithfully | Geo. R. Waterhouse