POLYZOANS. 27 



Archimedes laxus HALL. 



Archimedes laxa Hall, 1857: Proc. Am. As. Ad. Sci., vol. X, p. 178. 

 Helicopora archimediformis Claypolo, 1883: Quart. Jour. Geol. Soc , vol. 



XXXIX, p. 34, pi. iv, figs. 3-4. 

 Archimedes laxus Ulrich, 1890: Qeol. Sur. Illinois, vol. VIII, p. 580, pi. 



Ixiii, figs. 15-15a. 



Horizon and localities. Lower Carboniferous, Chester 

 limestone : Chester ( Illinois ). 



Lyropora retrosa MEEK & WORTHKN. 



Plate xxxlv, fig. 4. 



Fenestella (Lyropora} retrosa Meek & Worthen, 1868: Geol. Sur. Illinois, 

 vol. Ill, p. 504, pi. xv, fig. 1. 



Solid marginal support only known, the expanded, reticu- 

 late portion being always entirely removed. The two divisions 

 of the lateral support diverge at an angle of ninety degrees, 

 and are comparatively straight and slender. As in other 

 species of this group, they have their inner edges oblique and 

 not parallel to the plane of the fossil, while the minute, atten- 

 uated base of attachment is deflected toward the same side as 

 the inner edge of the lateral marginal supports. 



Horizon and localities- Lower Carboniferous, Burlington 

 limestone : Louisiana. 



Lyropora subquadrans HALL. 



Lyropora subquadrans Hall, 1857: Proc. Am. As. Ad. Sci , vol. X, p. 180. 

 Lyropora subquadrans Ulrich, 1S90: Geol. Sur. Illinois, vol. VIII, p. 582, 

 pi. Iviii, figs. 2-2e. 



Horizon and localities. Lower Carboniferous, Kaskaf-kia 

 limestone: Chester (Illinois). 



Lyropora quincuncialis HALL. 



Lyropora quincuncialis Hall, 1857: Proc. 4m As. Ad. Sci., vol X, p. 180. 

 Lyropoia quincuncialis Ulrich, 1890 : Geol. Sur. Illinois, vol. V11I, p. 583, 

 pi. Iviii, figs. 3-3d. 



Horizon and localities. Lower Carboniferous, Kaskaskia 

 limestone : Chester ( Illinois). 



