The CIFs (crystal information files) of two structures were submitted to topology studies performed with the TopCryst program . While C 4 used as template is designated with dia topology, C 9 was assigned with "4,4,4T6902-HZ" topology, and C 12 was identified with "sqc5532" topology. We note here that there are three allotropes with sqc topology in the SACADA database: sqc1427 (space group No. 125), No. sqc3051 (space group No. 114), and sqc6952 (space group No. 133) . The first two contain sp 2 carbon, while the third one shows only tetrahedral C(sp 3 ) with corner sharing tetrahedra. Structures with carbon squares are documented in the SCACADA database as crb topology with bct space groups (cf. No. 60-64 ). The novel C 9 and C 12 , not cataloged in databases, were subsequently deposited, curated, and then deposited in CCSD: C 9 and C 12 .