Prithvi which means the Earth in Hindi and Sanskrit is India’s short range surface-to-surface missile developed under the IGMDP by the Defense Research and Development Organisation (DRDO).

This project has 3 variants namely:

• Prithvi I (SS-150) – Army Version (150 km range with a payload of 1,000 kg)
• Prithvi II (SS-250) – Air Force Version (250 km range with a payload of 500 kg)
• Prithvi III (SS-350) – Naval Version (350 km range with a payload of 500 kg)
• Dhanush- Dhanush is reportedly a naval version of Prithvi which can be launched from Ships.

Here is what wikipedia says about the Prithvi variants

Prithvi I
Prithvi I class was a surface-to-surface missile having a maximum warhead mounting capability of 1,000 kg, with a range of 150 km. It has an accuracy of 10 – 50 metres and can be launched from Transporter erector launchers. This class of Prithvi missile was inducted into the Indian Army in 1994.

Prithvi II
Prithvi II class is also a single stage liquid-fuelled missile having a maximum warhead mounting capability of 1,000 kg, but with an extended range of 250 kilometres. It was developed with the Indian Air Force being the primary user. It was first test-fired on January 27, 1996 and the development stages were completed in 2004. The Prithvi II class of missiles are in the process of induction by the Indian Airforce. In a recent test, the Missile was launched with an extended range of 350 kilometres and improved Aided Inertial Navigation. The missile has the features to deceive Anti Ballistic Missiles.but on 24 september 2010 the launch of prithvi 2 was failed to take-off.This failure is the another part of the series of failures of Indian missile program. According to news sources the range is now increased to 350kms

Prithvi III
Prithvi III class (codenamed Dhanush meaning Bow) is a two-stage ship-to-surface missile. The first stage is solid fuelled with a 16 metric ton force (157 kN) thrust motor. The second stage is liquid fuelled. The missile can carry a 1,000 kg warhead to a distance of 350 km and a 500 kg warhead to a distance of 600 kilometres and a 250 kilogram warhead up to a distance of 750 kilometres. Dhanush is a system consisting of a stabilization platform (Bow) and the Missile (Arrow). Supposedly it is a customised version of the Prithvi and that the additional customizations in missile configuration is to certify it for sea worthiness. Dhanush has to be launched from a hydraulically stabilized launch pad. Its low range acts against it and thus it is seen a weapons either to be used to destroy an aircraft carrier or an enemy port. The missile has been tested from the surface ships many times.