The Treaty of Guadalupe Hidalgo, signed February 2, 1848, ceded Texas, New Mexico, and California to the US, completing American claims to land all the way across the continent. In return, the US assumed all monetary claims of US citizens against the Mexican government and paid Mexico $15 million. The West was now officially open and secure to Americans. Despite patriotism engendered by the war, sectional conflict grew more dramatic between 1846 and 1848. Not all of this was due to expansion.
They have a shell, made mainly of calcium carbonate, which is covered by skin. The skin conatins cells to help support and maintenance the skeleton, pigment cells, cells to detect motion on the animal's surface, and sometimes gland cells which secrete sticky fluids or even toxins.
The adults are recognizable by their (usually five-point) radial symmetry, and include such well-known animals as starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or stone lilies. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone.chinoderms have a mesodermal skeleton composed of calcareous plates or ossicles. Each one of these, even the articulating spine of a sea urchin, is composed mineralogically of a crystal of calcite. If solid, these would form a heavy skeleton, so they have a sponge-like porous structure known as stereom.