Baptismal Cross
The Baptismal Cross is a Greek Cross (+) superimposed on an X. The 'X' is not a saltire; rather it's the Greek letter chi, which is the first letter of the Greek word for Christ. (See also Iota-Chi Cross and Chi-Rho Cross.)
This blending of two cross symbols (see also Double Cross) was used in ancient Egypt as a symbol of the Ogdoad, the primeval forces of chaos in Egyptian mythology, represented as eight deities which existed before the creation of the sun god. (See also Taranis.)
Eight symbolises regeneration for many religions. It is the holistic number in Buddhism for the number of steps to end suffering.
This symbol is used as a symbol for Neo-Gnosticism and in Catholicism, where the eight arms represent both the age of baptism in the Church (within eight days of birth, and the eight days between Christ's entry into Jerusalem and his resurrection. The numerical value of the name of Yeshua (Jesus) in Koine Greek (Ἰησοῦς) is 888, making 8 a Christian 'super-number'.
The cross on the left is inlaid into the floor of the narthex at Park Ridge Community Church in Illinois, USA (parkridgecommunitychurch.org). It is a beautiful example of an ancient symbol that is perfectly suitable for a modern setting.
Their website explains the Baptismal Cross
...was selected because it calls us to remember two central elements of our faith life. It marks 'our going out and our coming in.'
First, upon entering the sanctuary, we are reminded of our baptism - our welcome into the beloved community by God's grace and through the waters of baptism. The symbol is actually two crosses—and so the eight 'arms' remind us that we come to this place from a wide variety of religious backgrounds and experiences.
When leaving the sanctuary, those same eight 'arms' send us outward to all points of the compass, to live out our faith in service to God's people wherever we may go.
The Park Ridge Community Church is affiliated to the United Church of Christ, but this cross is not restricted to their use, or indeed by any other Protestant or Catholic church.
For example, way over on the other side of the world in Orange, NSW, Australia we can see a Baptismal Cross on this grave headstone of an Orthodox Greek Cypriot.
The significance of Eight
Whether Pattée (image above) or not (image on the left), the symbol is called a Baptismal Cross in a Christian context, or asterisk (or star) for other uses.
The Groschen coin (on the right - click photo to enlarge) was introduced in 1271 by Duke Meinhard II of Tirol in Meran. The name groschen is derived from the double cross on the coin. Four of the eight pattée arms extend to the edge of the coin and the other four arms are shorter.
The Western glyph "8", as with the lemniscate symbol for infinity 
, is a never-ending line. Tracing the shape of the 8 differs from the circle, square, triangle etc., in that the line crosses itself in the centre. This crossing symbolises death. But the line does not stop there; it carries on into a new life, just as the Christian cross symbolises new life. This is why baptismal font is often octagonal.
The eight therefore is symbolic of life, death, and rebirth or regeneration. This is the meaning of the Baptismal Cross. (Another symbol for baptism is the Compostelan Shell.)
For related cross images, see the Asterisk and the eight-pointed Maltese Cross, Auseklis symbol, Christening Cross, Baptist Union Cross, Eternal Cross and St. John's Cross.)
Ref: Antiquities of the Christian Church, Times of Baptism
See also Cardinal Cross
