Matsya Purana — Cosmography of Śākadvīpa and Successive Dvīpas: Mountains
शिबिका च चतुर्थी स्याद् द्विविधा च पुनः स्मृता इक्षुश्च पञ्चमी ज्ञेया तथैव च पुनः कुहूः //
śibikā ca caturthī syād dvividhā ca punaḥ smṛtā ikṣuśca pañcamī jñeyā tathaiva ca punaḥ kuhūḥ //
The fourth tithi (Caturthī, the fourth lunar day) is called Śibikā, and it is again remembered as being of two kinds. The fifth tithi (Pañcamī) is to be known as Ikṣu; likewise, there is also the designation Kuhū.
This verse does not discuss Pralaya; it catalogs ritual-calendar terminology by giving traditional names for specific tithis (lunar days).
By identifying specific tithi-names and classifications, it supports correct timing for royal and household rites (vratās, donations, consecrations), a key duty in Puranic dharma to ensure ceremonies are performed on properly recognized lunar days.
Its significance is ritual-chronological: knowing tithi designations like Śibikā, Ikṣu, and Kuhū helps align temple worship schedules, fasts, and consecration-related observances with the proper lunar day as described in Matsya Purana calendrical guidance.