Radical 213

Radical 213 meaning "turtle" is one of only two of the 214 Kangxi radicals that are composed of 16 strokes.
In the Kangxi Dictionary there are only 24 characters to be found under this radical.
In Taoist cosmology, 龜 is the nature component of the Ba gua diagram 坎 Kǎn.

Variant characters

There are a number of variant characters that appear different but mean the same thing:

By typefont

As a CJK Unified Ideograph, has seven separate reference glyphs shown in the Unicode code charts, no two of which are exactly identical:

"G", for Traditional Chinese in Mainland China, as in the Guobiao standard GB/T 12345
"H" for use in Traditional Chinese
"T" for use in Traditional Chinese
"J" for Japanese kyūjitai
"K" for use in Korean hanja
"KP" for use in Korean hanja
"V" for use in Vietnamese Hán Nôm

As such, appearance may subtly vary between fonts intended for different regions:

In Unicode

Due to an especially large number of variant forms associated with Radical 213, an exceptionally large number of Unicode characters exist displaying variants of the character itself, as opposed to derived characters.

Literature

Leyi Li: "Tracing the Roots of Chinese Characters: 500 Cases". Beijing 1993,