The lotus, one of the Eight Treasures of Buddhism is symbolic of purity and became one of the most popular themes in Rhinoceros horn carving.
The inclusion of a large crab to the interior is also a fairly common theme. The stalk of rice. he held in its pincers is homonymous in Chinese with the word for 'harmony' and together with the crab, xie and the grain, sui, they form the rebus suisui hexie, 'may you have a harmonious marriage year after year'. The theme is further discussed by J. Chapman, The Art of Rhinoceros Horn Carving in China, Hong Kong, 1999, p. 188.
Compare the present cup with one in the Chester Beatty Library Collection, illustrated by J. Chapman, Ibid, p.166, fig. 207.