1) Neritid 2) Neritid gastropod 
Neritina is a genus of small aquatic snails with an operculum, marine, brackish water, and sometimes freshwater gastropod mollusks in the family Neritidae, the nerites. Neritina is the type genus of the tribe Neritinini. == Species == Species in the genus Neritina include: Species brought into synonymy: ...
• (n.) A genus including numerous species of shells resembling Nerita in form. They mostly inhabit brackish water, and are often delicately tinted. • (n.) A genus including numerous species of shells resembling Nerita in form. They mostly inhabit brackish water, and are often delicately tinted.
Ner`i·ti'na noun (Zoology) A genus including numerous species of shells resembling Nerita in form. They mostly inhabit brackish water, and are often delicately tinted. 
[n] - ornately marked and brightly colored snails of brackish waters
noun ornately marked and brightly colored snails of brackish waters