In snakes, the paraventral scales are the longitudinal rows of dorsal scales

Dorsal scales

In snakes, the dorsal scales are the longitudinal series of plates that encircle the body, but do not include the ventral scales.When counting dorsal scales, numbers are often given for three points along the body, for example 19:21:17...

 that contact the ventral scales

Ventral scales

In snakes, the ventral scales are the enlarged and transversely elongated scales that extend down the underside of the body from the neck to the anal scale. When counting them, the first is the anteriormost ventral scale that contacts the paraventral row of dorsal scales on either side...

. These are the first rows of dorsal scales on either side of the body and are usually slightly larger than the scales located more dorsally. In species that have mostly keeled scales

Keeled scales

Keeled scales refer to reptile scales that, rather than being smooth, have a ridge down the center that may or may not extend to the tip of the scale, making them rough to the touch...

, the paraventrals are usually smooth or only weakly keeled.

The term paraventral may also refer to the area on either side of the ventral scales.