„ BbYO^OA. 139' 



Eurydictya.] 



t 



Eurydictya multipora ? Hall, sp. 



PLATE VI, FIGS. 9-11 ; PLATE VII, FIGS. 24 and 29-31 ; PLATE XIV, FIGS. 9-11. 



9 Phoenopora multipora Hall, 1851. Geo. Lake Sup. Land Dist., vol. ii, p. 206. 



Phcenopora (?) multipora Ulbich, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 171. 



Eurydictya multipora Ulrich, 1890. Geol. Surv. 111., vol. viii, p. 520. (Referred to new genus only.) 



Zoarium forming irregularly divided vsride fronds, 6 to 20 mm. in width, or simple 

 undulating expansions, or a combination of the two. The Minnesota example figured 

 on plate XIV is a fragment of a slightly undulating expansion, 0.7 mm. to 1.5 mm. 

 thick, that must have been no less than 20 mm. wide. The others are of less width, 

 and one (plate VII, fig. 24) deviates so widely from the ordinary growth that it was 

 at first believed to belong to Bhinididya mutahilis yar. major. 



Surface with irregularly distributed small maculss, often very inconspicuous and 

 scarcely interrupting the regularity of the longitudinal ridges. In other cases they 

 may appear as smooth solid spots, fuUy 1 mm. in diameter. As a rule they give one 

 the impression of a variable number of elongate zooecia filled with a solid deposit of 

 calcareous material. Zocecial apertures subelliptical, more or less oblique, (generally 

 more so than in fig. 11, plate XIV) with a slight peristone, strongest at the posterior 

 margin, arranged between rather prominent, granulose, longitudinal ridges, seven- 

 teen or eighteen in 5 mm.; also in curved diagonal series, but these are never very 

 regular and frequently turn into transverse rows. Measuring transversely, from 

 twenty-three to twenty-six of the longitudinal rows may be counted in 5 mm. The 

 width of the interspaces is usually about equal to the diameter of the apertures. 

 When the latter are partially filled with the clayey maxtrix, they may appear as of 

 subquadrate shape, with the interspaces thinner than usual. In the narrow or basal 

 part of the fronds, the spreading ^edges are sharp, non-poriferous, and striato- 

 granulose, while several of the marginal rows of the zocecial apertures may be 

 directed obliquely outward. 



Vei»tical sections show that the primitive cell is rather high, short, and has thin 

 walls. These curve over it to a point marking the beginning of the vestibular por- 

 tion of the tube, when they bend sharply outward. At the same time the interspaces 

 (walls) are greatly widened, and three to five shallow vesicles are developed in direct 

 sequence. Above these the interspaces are solid and seemingly structureless, if we 

 except a dark line running lengthwise through them. No diaphragms observed. 



Tangential sections may present one or all of three distinct phases or stages in 

 the development of the zoarium. Their exhibition depends upon the distance from 

 the median laminae at which the zooecia are cut by the section. In the first or deep- 

 est part of the section, the zooecia are quadrate, thin-walled, and arranged in regular 



