Descartes snark
{{Infobox graph
| name = Descartes snark
| image = 200px
| image_caption = Image of a Descartes snark.
| namesake = Blanche Descartes
| vertices = 210
| edges = 315
| girth = 5
| chromatic_index = 4
}}
In the mathematical field of graph theory, a Descartes snark is an undirected graph with 210 vertices and 315 edges. It is a snark, a graph with three edges at each vertex that cannot be partitioned into three perfect matchings. It was first discovered by William Tutte in 1948 under the pseudonym Blanche Descartes.{{citation
| last = Descartes | first = Blanche | author-link = Blanche Descartes
| doi = 10.2307/3610702
| journal = The Mathematical Gazette
| jstor = 3610702
| mr = 26309
| pages = 67–69
| title = Network-colourings
| volume = 32
| year = 1948}}
A Descartes snark is obtained from the Petersen graph by replacing each vertex with a nonagon and each edge with a particular graph closely related to the Petersen graph. Because there are multiple ways to perform this procedure, there are multiple Descartes snarks.