Of peculiar importance for the differentiation of the numerous genera of the #Spyroidea# are the basal feet or the descending and diverging apophyses, which are developed from the base of their cephalis. In general they exhibit the same typical shape which we find in the #Plectellaria# as well as in the #Cyrtoidea#, and which we regard therefore as an important common character of the majority of NASSELLARIA. We may therefore distinguish here also the three primary, and the other ones as secondary feet. The three primary feet, or the "cortinar feet," are the same that we found in the Plagonida and Plectanida, in _Cortina_ and _Cortiniscus_ among the #Stephoidea#, and in the majority of #Cyrtoidea#. They also reappear in the same characteristic disposition and connection with the basal plate of the cephalis, in the majority of #Spyroidea#. The odd caudal foot (_c_) is the lower prolongation of the dorsal rod of the sagittal ring, which is prolonged upwards into the apical horn. The two paired pectoral feet, however (_p'_, _p''_), are the descending prolongations of the coracal rods (_e_) which separate the jugular pores (_i_) from the cardinal pores (_k_) of the cortinar plate (compare Pl. 95, figs. 2-6). The three cortinar feet are nearly equally developed in the majority of #Spyroidea# (compare Pls. 84, 89). But often the odd caudal foot exhibits a different shape from that of the two paired pectoral feet, and in many genera of the group it becomes more or less rudimentary. It has quite disappeared in the subfamily Dipospyrida (Pl. 85); here the two pectoral feet only are developed (often excessively), and are usually opposite in the frontal plane. Such dipodal forms, very common in the #Spyroidea#, are never found in the #Cyrtoidea#.