Spkcies of the Keokuk Gkoup. 169 



Reticulum. The quadrate meshes are remarkably uniform in size and 

 arrangement. Assuming that the vertical spicular bands of the first order 

 lie along the angles made by adjoining prismatic faces, a given square of the 

 first order measures about 20 mm. on a side, varying with the slight curvature 

 of the surface, and with the upward expansion of the prism-faces. The sub- 

 division of these quadrules is carried out with regularity to the fifth degree, 

 and even in some of these pentameres there is evidence of a division into ulti- 

 mate quadrules. Some of the specimens indicate that the surface, in 

 its original condition, was fenestrated by the slight projection of the 

 principal lamellae. 



Dimensions. The apertural width of the specimen figured is 120 mm. ; 

 its diameter where narrowest is aboiit 90 mm. and the incomplete cup has a 

 length of 115 mm. which was probably somewhat more than one-half its 

 entire length. 



Locality. In the calcareous shales at Crawfordsville, Indiana. 



LEBEDICTYA, gen. nov. 



Large obconical cups, perhaps somewhat unsymmetrical by reason of more 

 rapid growth on one side, probably expanding from a subacute base. Surface 

 obscurely prismatic and cancellated by short projecting spicular lamellae. 

 Aperture crowned by an erect fringe of long marginal spicules. 



Type, Lebedictya crinita, sp. nov. 



Lebedictya cbinita, sp. nov. 



Plate lviii, Fioa. 1, 3 ; Plats lls, Fios. 1, 2 ; Platb lxi, Fio. 5. 



Sponge cyathiform, expanding with apparently slight asymmetry from a 

 narrow base. This asymmetrical growth is especially evident in one specimen 

 which not only shows a notable difference in the size of the two sides, but 

 along the apertural margin, which is distinctly retained, indicates a rapid 

 multiplication of the spicular net- work on the longer side of the cup. The 

 surface is rendered obscurely prismatic by the predominance of certain ver- 

 tical skeletal ridges which, near the aperture, lie about 25 mm. apart. The 

 horizontal ridges do not attain so great size, but the prevailing quadrules are 

 nevertheless large, measuring from 12 to 15 mm. on a side, and are variously 

 subdivided. All these vertical and horizontal spicular bands are erect and 

 form a moderately deep surface reticulation. There may also have been 

 minute tufts at the intersections but the evidence of them is not very clear. 

 The fenestration of the exterior of the cup is similar to, but much less 



