956 



THE VOYAGE OF H.M.S. CHALLENGER. 



Synopsis of the Genera of Semantida. 



' Two basal pores, . 



I. Subfamily 



Semantiscida. 

 Basal ring without typical, 

 regularly disposed basal 

 feet (no cortinar feet). 



IL Subfamily 



CortLniscida. 

 Basal ring wtli typical, - 



regularly disposed basal 



feet (cortinar feet). 



Only two, four, or six basal 

 pores (no dorsal and - 

 ventral pores). 



Four basal pores, . 

 Six basal pores, 



Besides four basal pores, also apical pores or dorsal and 

 ventral pores along the whole ring, 



Three basal feet. 



Four basal feet. 

 Six basal feet. 



{ 



One odd caudal foot and 

 two paired lateral feet, 



Two sagittal and two latera 

 or pectoral feet, 



Two sagittal, two pectoral 

 and two tergal feet. 



407. Semantis. 



408. Semantrum. 



409. Semantidium. 



410. Clath rocireus. 



411. Cortiniseus. 



412. Stephaniscus. 



413. Semantiscus. 



Subfamily 1. Semantiscida, Haeckel. 

 Definition. — S emantida without typical basal feet or cortinar feet. 



Genus 407. Semantis, n. gen. 



Definition. — S emantida with two basal pores (or jugular pores), without 

 typical basal feet. 



The genus Semantis, the most primitive and the oldest of the Semantida, is of the 

 greatest morphological interest, as the first form of Stephoidea which produces 

 gates or pores by communicating branches, and therefore the probable ancestral form not 

 only of this family, but of the greater number of all S t e p h o i d e a, and perhaps even 

 of all Spyroidea and C y r t o i d e a. Semantis arises from Archicircus by the pro- 

 duction of two pairs of lateral branches from the basdar rod of the sagittal ring, one 

 anterior pair of clavicular rods, and one posterior pair of coracal rods. By junction of the 

 cla\'icular and coracal rod on each .side arises a left and a right pore, the "jugular pore or 

 jugular gate." 



1. Semantis hiforis, n. sp. (PI. 92, fig. 2). 



Sagittal ring obliquely ovate, nearly trapezoidal, with six pairs of short mammillated knobs or 

 branches ; dorsal rod straight, vertical, with two pairs of knobs, ventral rod strongly convex, also with 



' iSe7rianiw= Signet-ring ; <jr,f/,ct.ini;. 



