66 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



spines on the others. The ovicell is hyperstomial, not closed by the 

 operculum, buried in the distal zooecium, large globular, smooth. 

 Each zooecium bears theoretically two oblique triangular avicularia 

 with a pivot or with denticles, placed at the level of the apertures of 

 the adjacent zooecia; the beak is very pointed and arranged in ac- 

 cord with the peristome of the adjacent zooecia, as well shown 

 in Gabb and Horn's figure. 

 Measurements. — 



~ \Lz= 0.75-0.85 mm. . f ha=02 mm. 



Zooeciumj &=Q ^ g mm Aperturaj ^otf-42 ^ 



10-13 zooecia in 4 sq. mm. 



Variations. — The dimensions are quite variable. On the vigorous 

 specimens the zooecial length attains 1 mm and the width 0.5 mm. 

 The number of costules varies accordingly for on the long zooecia 

 it is about 20 and on the shortest it is only 10. 



When the zoarium develops regularly the zooecia remains quite 

 elliptical ; but when the gemmation is deranged, they are much con- 

 stricted and become fusiform. 



The avicularia do not have the theoretic regularity, for this de- 

 pends exclusively on the regularity of the gemmation. When this 

 becomes irregular, the avicularia disappear or are oriented dif- 

 ferently, then some zooecia have a single avicularium and others are 

 deprived of them. 



Lang's figure 72 is incorrect, for the avicularia do not belong to 

 the zooecium, where they appear to be placed. Their base is always 

 placed on the adjacent zooecium, and it is the beak only that is more 

 or less united with the distal part of the peristome. The avicu- 

 larium is always placed below the transverse median axis of a 

 zooecium. It develops only if there is an aperture of a neighboring 

 zooecium at its height. If through irregular gemmation there is 

 no aperture, it does not develop at all. This phenomenon of inter- 

 connection is remarkable, but it is not unique, for it has been ob- 

 served in other genera of the Cheilostomata. 



The costules are irregularly decorated. The pelma and pelmatidia 

 are often absent. The proximal pelma is rather constant; the distal 

 pelmatidium often is transformed into a true pelma. 



The epicalcification that occurs around each zooecium is impor- 

 tant. It is rather regular and envelops the distal spines, which 

 disappear, become invisible, or leave only faint traces. It is fre- 

 quently more intense at the base of the zooecia. According to its 

 thickness, it diminishes the length of the spines when it spreads over 

 the frontal. It rarely fills in the cellular intervals. 



The aperture is not rigorously orbicular. It is somewhat elon- 

 gated and restricted laterally ; its proximal border is simply convex. 



