_Fig._ 11. is a group of Barnacles of a conical form, composed of purplish tubes like small quills. _Fig._ 11.a represents one of the same, with a view of its base, from the collection of Mr. Peter Collinson, F.R.S. This was brought from the East Indies. The insides of these shells have the appearance of the spongy parts of bones. _Fig._ 12. is called the Tortoise-wart Barnacle, being often found upon that animal. This shell is of a plano-convex shape, and looks like polished ivory. The divisions between the valves represent a star with six points. If these shells are put into soap lees, they will in a few hours separate into six pieces or valves, each shelly valve having two ears, like the scallop-shell: so that this species has its valves connected by membranes, instead of testaceous sutures, as most of the others have. _Fig. 12. a_ represents the under part of the same shell. _Fig._ 13. This shell is marked with six rays like a star, as the former; but is much deeper in proportion to its diameter. Several of this kind were found sticking to a crab, that was lately brought from the island of Nevis; from whence I have called it the American Crabs-wart. _Fig._ 14. is called the Side-mouth Barnacle. This was found on the southern coast of Africa, near the Cape of Good Hope, where it adheres to a particular species of striated purple muscle. _Fig._ 14.a represents two of the opercula of this Barnacle remarkably horned. The shell of this is very thin; but its obliquity may probably be owing to its situation. _Fig._ 15. This egg-shaped Barnacle with a small mouth is found in clusters sticking to the Buccinum tribe of shells in the West Indies. _Fig._ 16. is the Cornish Barnacle, shaped like a cone, and with a small mouth. This is described and figured by the Revᵈ. Mr. William Borlase, F.R.S. in his Natural History of Cornwall, lately published. _Fig._ 17. This is the common English Barnacle, that is found in such plenty upon all rocks and shells round this island. From the animal of this, examined in the microscope, I have taken the character of the fish of the Barnacle genus. _Fig._ 18. This I have called the Limpet-shaped Barnacle, from its likeness to some species of that shell. I am indebted to our late worthy member, Mr. Arthur Pond, for this shell, who assured me it was brought to him from Greenland. It was, with several more, found sticking to a very large species of muscle.