[*] 92. The following peculiarities in case-forms of the Fourth Declension require notice:— [*] a. A genitive singular in -ī (as of the second declension) sometimes occurs in nouns in -tus: as, senātus , genitive senātī (regularly senātūs ). [*] b. In the genitive plural -uum is sometimes pronounced as one syllable, and may then be written -um: as, “ currum ” (Aen. 6.653) for curruum . [*] c. The dative and ablative plural in -ŭbus are retained in partus and tribus; so regularly in artus and lacus , and occasionally in other words; portus and specus have both -ubus and -ibus. [*] d. Most names of plants and trees, and colus, distaff, have also forms of the second declension: as, fīcus, fig, genitive fīcūs or fīcī. [*] e. An old genitive singular in -uis or -uos and an old genitive plural in -uom occur rarely: as, senātuis, senātuos; fluctuom. [*] f. The ablative singular ended anciently in -ūd (cf. § 43. N. 1): as, magistrātūd.
[*] 92. The following peculiarities in case-forms of the Fourth Declension require notice:— [*] a. A genitive singular in -ī (as of the second declension) sometimes occurs in nouns in -tus: as, senātus , genitive senātī (regularly senātūs ). [*] b. In the genitive plural -uum is sometimes pronounced as one syllable, and may then be written -um: as, “ currum ” (Aen. 6.653) for curruum . [*] c. The dative and ablative plural in -ŭbus are retained in partus and tribus; so regularly in artus and lacus , and occasionally in other words; portus and specus have both -ubus and -ibus. [*] d. Most names of plants and trees, and colus, distaff, have also forms of the second declension: as, fīcus, fig, genitive fīcūs or fīcī. [*] e. An old genitive singular in -uis or -uos and an old genitive plural in -uom occur rarely: as, senātuis, senātuos; fluctuom. [*] f. The ablative singular ended anciently in -ūd (cf. § 43. N. 1): as, magistrātūd.