A group of artists, so-named because they exhibited their work in the Crypt of the Mariners' Church, St Ives. The group was initially made up of Sven BERLIN, Peter LANYON, Guido MORRIS, Phil Whiting and Bryan WYNTER. Their first exhibition took place in September 1946. The catalogue was printed for them by Guido MORRIS, with Borlase SMART being the opening speaker for the occasion.

The initial exhibition raised not only eyebrows but brickbats from more traditional artists, spurred-on by Harry ROUNTREE (1878-1950, the painter, illustrator and caricaturist) who called on the frankly Modernist group to drop the 'French rot' and get back to sweet sanity. However, by August 1947 Wilhelmina BARNS-GRAHAM had joined the group, and seventeen artists altogether showed in the Crypt, including Barbara HEPWORTH, Denis MITCHELL, Alice MOORE, Ben NICHOLSON, Misome PEILE, John WELLS and Bryan WYNTER.

The final Crypt Group exhibition included work by David HAUGHTON, Patrick HERON, Adrian RYAN and Kit BARKER in addition to all the previously mentioned exhibitors. It was held in August 1948, opened by Francis Watson. 

By February 1949 the new PENWITH SOCIETY of Arts in Cornwall was founded by a group of nineteen, which included the whole of the Crypt Group and others sympathetic to the aims of those who had resigned from STISA.  It was agreed that the Penwith Society be founded in memory of Borlase SMART (who had died in November 1947), and invited Herbert READ to be the first President, with Leonard John FULLER as Chairman and David COX Honorary Secretary.  Unlike STISA, the Penwith Society included both artists and craftsmen among its members.