BRYOZOA. 569 



ARCHIMEDES NEGLIGENS Ulrich. 



PL LXm, Fig. 7-7a. 



Axis slender, lax, appearing delicate, faintly fusiform, at least 

 ten cm. in length; volutions moderately irregular, varying in 

 different examples from 3.6 to 4.5 in two cm. It is only in rare 

 instances that there are more than four in that space. Shaft 

 thin, slightly spiral. Fenestrated expansion from one to two 

 cm. wide, making an angle of about 75 with the axial line. 

 Branches slender, straight, 24 or 25 in one cm.; on the obverse 

 with very faint carina separating the two rows of zooecia, of 

 which there are about 26 in five mm. Apertures small, with 

 peristome. Fenestrules elliptical here, quadrangular on the re- 

 verse, a little longer than wide, about seven in one cm. Dis- 

 sepiments about half as wide as the branches. 



The axis of this form cannot be confounded with those of any 

 other species known to me from this horizon. They resemble A. 

 terebriformis, of the Chester group, but the shaft is not swollen 

 below the flange, and the whole has a more delicate aspect. 

 Diani. of shaft of strongest ex. 1.5 mm.; No. of vol. in 2 cm., 4. 

 " smallest " 0.7 " " " 4. 



average " 1.0 " " " 3.8. 



another " 1.0 " " 4.6. 



Position and locality: Keokuk group, Bentonsport and 

 Keokuk, Iowa. 



ARCHIMEDES GRANDIS Ulrich. 



PI. LXTTT. Fig. 10. 



Axis very large and strong, the largest example seen, though 

 incomplete at both extremities, being nearly eighteen cm. long, 

 and making one volution to each cm. Of two other examples 

 one makes eight the other nine turns in ten cm. The shaft is 

 comparatively slender, and gradually spreads from the flattened 

 top of a flange into the smooth under side of the succeeding 

 flange, presenting on a large scale very nearly the appearance 

 noticed in A. invaginatus of the Chester group. Fenestrated 

 frond about five cm. wide, forming an angle of from 60 to 65, 

 with the axial line. Branches slender, 23 or 24 in one cm., 

 71 



