NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



199 



tally, and enlarged proximally; the opesium is oval shaped and a little oblique. 

 The length of the zooecium is 0.60 to 0.70 nun. 



Affinities. This species may be distinguished from IleteroceHa fragilis De- 

 france, 1820, by its greater micrometric dimensions, its straighter zooecia, and its 

 smaller septulae. 



Occurrence. Vicksburgian (Marianna limestone) : Salt Mountain, 5 miles 

 south of Jackson, Alabama (common). 



Cotyj>fs.Ci\t. No. 64251, U.S.N.M. 



FIG 52. Fam'.y Eucrutiidae Hincks, 1SSO. 



A-G. Evcratca chclata Linnaeus, 1758. A. Free larva viewed in profile ; the terminal bud 

 is much reduced, the aboral face well developed, and the oral face completely flat, X 75. 

 B. Aboral face of larva showing the very simple terminal bud and the stomach visible even from 

 the side, X 75. C. Larva, oral face, showing the trilobate form of the stomach, X 75. 

 (A-C after Barrois, 1877.) c, corona; CD, digestive cavity; est, stomach; i, aboral face; ph, 

 pharynx; pi, ciliary plume; o, mouth of the gastrula ; s, oral face; 6, furrow separating the 

 aboral mass and funnel-shaped side ; si. furrow separating the terminal bud and the lower por- 

 tion of the aboral face; vt, terminal bud. D. Zoarium, natural size. B. Portion of a zoariuui, 

 X 50, showing the structure of the zooecia and method of branching (c. lir) just below the 

 opesia (/;) and the creeping branches (cr. br.) given off from the sides of the zooecia; (op) 

 operculum. (After Robertson, 1005.) F. Sketch, X 50. showing ovicell (oe) on a small aborted 

 zooecium. (After Hincks, 18SO.) G. Anatomical structure of a zooecium. (After Milne-Ed- 

 wards, 1838.) a, zooecium; 6, opesium; c. opercular valve; d, tentacular shea Hi ; e, ri Hated ten- 

 tacles; /. stomach; g, stomachic coecum ; Ji. anus; i, retractor muscles of the polypide. 



Family EUCRATIIDAE Hincks, 1880. 



Zoarium forming slender, branching, phytoid tufts. Zooecia uniserial or in 

 two series placed back to back ; expanding from the base upwards, with a terminal 

 or subterminal and usually oblique opesium. Neither avicularian nor vibracular 

 appendages known. Ovicell globose, hyperstomial. (Robertson.) 



