THR MORPHOLOGY OP THE CHEILOSTOMATA. 327 



buddiug. One of these (z/) is on the distal side of the 

 ancestrula, and the other (not drawn) is on its apparent left 

 side. On each of the five oral spines of these zooecia is a 

 minute calcareous lobe resembling those of the marginal 

 spines of the ancestrula. The lobes may be indicated by 

 still smaller projections on the oral spines of the other 

 zooecia. 



In all the ordinary individuals there occur, on the proximal 

 side of the operculum, a pair of delicate, membranous, 

 elongated structures {sj).), which are described by Hincks 

 (1880, p. 186) as vibraculoid setse. Smitt^ ascribes to them 

 a sensory function. 



The structures in question have no claim to be regarded as 

 vibracula. There is no trace of any muscles connected with 

 them, and there can be no doubt that they continue the line 

 of the oral spines. 'J'his line is, in reality, prolonged all 

 round the zooecium, the succeeding spines [sp.') being delicate 

 membranous papillte which barely project above the calcareous 

 surface, and are obviously in series with the oral spines and 

 the "vibraculoid setae." The base of each papilla is a pore in 

 the calcareous frontal wall. Comparison with the ancestrula 

 and with the calcareous lobes of the oral spines of the younger 

 zooecia seems to indicate that the membranous papillas, together 

 with the oral spines, correspond with the marginal spines of 

 the ancestrula. The calcareous lobes of that individual are, 

 in consequence, the representatives of the bars which have 

 united to form the frontal wall of the ordinary zooscia, while 

 the scutum-like spine of the ancestrula is probably the 

 equivalent of one of the denticulated lobes on the other 

 spines. 



It has usually been assumed that the radiating series of 

 pores correspond with the slits between the bars. This is 

 certainly the case in C. philomela (fig. 8); but in C. 

 radiata (fig. 7) there can be no doubt that the pores are in 

 the same radii as the membranous marginal spines. I can 



1 " Floridan Bryozoa," II, ' K. Svenska Vet.-Ak. Haiidl.,' xi, 1873, No. 4, 

 p. 22. 



