BRYOZOA—CRYPTOSTOMATA. 155 



LXXI. Bactkopora Hall. 

 Like Rhombopora, but simple or only slightly branched, and 

 with lower extremity pointed. Dev.-Miss. 



124. B. simplex Ulrich. (Fig. 208, d.) Mississippian. 



Surface with transversely elongated monticules, appearing often 

 like annulations ; apertures oval to subcircular ; narrow interspaces 

 with a single or double row of small acanthopores ; average size 

 1.5 mm. in diameter by 18 mm. in length. 



Keokuk of Iowa, Illinois, and Missouri. 



LXXI I. Streblotrypa Ulrich. 

 Ramose, slender, and solid, frequently bifurcating, with long 

 tubular zocecia diverging from the center, with hemisepta (inferior 

 one best developed) and regularly elliptical 

 apertures with peristomes usually arranged 

 in longitudinal series; one to fifteen small 

 pits below the apertures, and occasionally 

 very small acanthopores. 



Fig. 209. streblotrypa i 2 $. S. hamiltonensis (Nicholson). (Fig. 



.8. (After HaM and Simp- 2 °^ DeVOmC - 



son x Apertures between prominent wavy lon- 



gitudinal ridges, alternating in position in 

 adjoining ranges, and having two angular pits between the aper- 

 tures of each row. 



Hamilton of Western New York and Ontario. 



126. S. nicklesi Ulrich. (Fig. 208, e.) Mississippian. 



Apertures small, between three straight longitudinal ridges, 

 alternating; peristomes strongest anteriorly; interspaces with 

 from nine to fifteen small pores in two or three rows. 



Chester of Illinois and Kentucky. 



LXXIII. Ptilodictya Lonsdale. 



Simple, unbranched, lanceolate or falciform frond, articulating, 

 with small basal expansion, and having zocecia on both sides except 

 the margin ; zocecia narrow oblong-quadrate and arranged longi- 

 tudinally in the young and with additional variously formed zocecia 

 added in the adult; walls of vestibules thick, solid, and with a 

 double row of minute dots. Ord.-Dev. 



