NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



517 



HASWELLIA GRACILIS, new species. 



Plate 66, figs. 8-10. 



Description. The zoarium is free, cylindrical, slender. The zooecia are dis- 

 posed all around the zoarium ; they are quite long and indistinct ; the frontal is a 

 thick tremocyst with small, numerous pores. The peristome is salient, almost per- 

 pendicular to the zoarium ; the peristomice is orbicular ; the peristomie is invisible 

 exteriorly, but it is as long as the zooecia. The spiramen is a small, salient, oblique 

 tube placed on the median zooecial axis just below the peristome. 



Measurements. Apertura 



Ue=0.09 mm. 



Zooecia. Z2=0.75-1.50 mm. 



avd 



Affinities. In spite of its very simple structure this species has necessitated 

 long study. Success 

 with the longitudinal 

 sections (fig. 9) has 

 permitted us to clas- 

 sify it generically. 

 The spiramen is 

 higher than the peri- 

 stomie and quite dis- 

 tant from the aper- 

 tura. 



This species much 

 resembles the recent 

 Porina proboscidea 

 Waters, 1888. It dif- 

 fers from it in its 

 much smaller micro- 

 metric dimensions 

 and in its zooecia dis- 

 posed all round the 

 zoarium and not on 

 one side alone. It 

 sometimes has a small 

 avicularium placed in 

 the vicinity of the 

 apertura. 



FIG. 151. Genus Semihasu-ellia Canu and Bassler, 1917. 



A-C. Semihaswellia proboscidea Waters, 1889. A. Zoarium natural size. 

 B. Fragment of branch with ordinary and ovicelled zooecia, X 25. C. Pos- 

 terior face without zooecia, X 12. (A-C after Waters, 1889.) 



ai'd, dorsal avicularium ; a;/, frontal avicularium; ov, ovicell; pis, exte- 

 rior orifice or peristomice, never closed by the operculum; s, sulci; sp, spi- 

 ramen. 



Occurrence. Middle Jacksonian (Castle Hayne limestone ): Wilmington, North 

 Carolina (very common). 



Holotype.Csit. No. 64164, U.S.N.M. 



Genus SEMIHASWELLIA Canu and Bassler, 1917. 



1917. Semihaswellia, CANU and BASSLEB, Synopsis of American Early Tertiary Clieilostonie 

 Bryozoa, Bulletin 96, United States National Museum, p. 58. 



The zooecia are disposed only on one side of the zoarium ; the dorsal bears only 

 avicularia. The frontal and the dorsal are of the same nature and are formed of 

 a tremocyst with sulci. 



