﻿AbstractThis study deals withUlnariaspecies found and described from two regions of China with large climate differences during the period of 2014–2022. The first region, located in the Wuling Mountains and Hunan province, has a subtropical climate and the second in Qinghai, a northwest province of China, has a highland continental climate which is characterized by a cold and long winter and warm, short summer. Previously there were nine newUlnariaspecies published from the first region. This study describes 14 additional newUlnariataxa, nine of which were found in the first region and five of which were found in the second region. A key to theUlnariaspecies that have been described from China is provided. The main morphological characteristics for 63Ulnariataxa are summarized in Appendices which allow the division of theseUlnariataxa into three groups: the seven members of group one all possess both uniseriate striae and valve marginal spines, the 42 members of group two all possess uniseriate or mostly uniseriate striae but without the valve marginal spines, and the 14 members of group three all possess mostly biseriate striae and without valve marginal spines. To summarize the morphological characters of the publishedUlnariataxa and 14 taxa described in this study several conclusions for the characterization ofUlnariaare drawn: 1) each cell has two valve-appressed, long plate-like plastids; 2) living cells of manyUlnariaspecies often lie in girdle view on a slide because they have deep mantles and some copulae associated with either the epivalve or the hypovalve so that the cell depth is often larger than the valve width; 3) the basic structures forming a valve include sternum, virgae, and vimines/viminules; 4) the valvocopula is a closed hoop which has a similar ultrastructure in allUlnariataxa but differs from the other copulae in structure; 5) the configuration of girdle bands is a common condition; 6) the life history ofUlnariacan be divided into the four series of successive stages: auxospore, initial cell, pre-normal vegetative cell, and normal vegetative cell, which is very similar to the life history ofHannaeainaequidentata(Lagerstedt) Genkal and Kharitonov; 7) the closed valvocopula is proposed as a definition character for the genusUlnariabecause demonstrating all girdle bands closed is impracticable.