12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



be seen with the naked eye. These plates and their divisions are 

 SO distinct that I am forced to beUeve that where the pubHshed generic 

 diagnosis says " basal pieces 3, forming together a low cone," it was 

 due to a typographical error, and should have read " 3." At the 

 interior surrounding the cone there is considerable indication of a 

 division of the basal ring into five plates, which was the occasion 

 of Shumard's doubtful statement of " primary radials (basals in 

 our terminology as already explained), 5?"; but the suture lines 

 are not sufficiently distinct to furnish a definite sketch of their posi- 

 tion. The floor of the calyx at the median portion of the base is too 

 thin to permit any manipulation of the plates at the exterior, where 

 no trace of the boundary of the cone, nor of any interbasal sutures, 

 can be seen. 



The presence of the tripartite cone is fully confirmed by two other 

 specimens, in one of which the cup has been fractured vertically in 

 such a way that the median part of the base is left intact and free from 

 matrix on both surfaces. This contains the cone in all respects similar 

 to that of the Shumard type, with its three plates completely separated 

 by sutures. Not only so, but the line of fracture of the thin base 

 follows about half the perimeter of the infrabasal circlet, which is 

 thus separated from the surrounding basals and left projecting so that 

 its outline is perfectly defined, leaving no doubt that it passed through 

 to the dorsal surface. I have been able to photograph this specimen 

 from both aspects, and also the interior of the Shumard type, so that 

 the structures are accurately shown without any retouching as to 

 these details (pi. 2, figs. 2, 7, 8). In the third specimen (fig, loa) 

 the cone also appears very much as in the Shumard type, but owing 

 to some distortion of the calyx does not yield so clear a photograph. 



Two other specimens in which the interior is free from the matrix 

 show the raised contour of the cone, but not the divided plates, the 

 sutures being completely fused. Viewed by transmitted light through 

 the thin base, the obtuse outline of the infrabasal circlet, similar to 

 that which is exposed in the fractured specimen, can be fairly well 

 seen. In all these interior views there are lines more or less obscured 

 by fusion which in my opinion indicate a division of the plates sur- 

 rounding the cone into five. Upon two other specimens filled with 

 hard matrix, I ground and poHshed the base at the dorsal side, and 

 found the sutures partially indicated in both, together with the 

 rounded outline of the infrabasal circlet. In one of these I was able 

 to locate four of the interbasal sutures, leaving the position of the 

 fifth obvious. By means of these two specimens, supplementing 



