150 



Report of the State Gkologist. 



PLATE IV. 



Manticockkas sororium, sp. nov. 



Figures 1, 2, 3, 4, 5. These figures illustrate the variation which exists in the 

 ornament of this species during its early phases of growth. The 

 specimens are all gutta-percha squeezes from moulds artificially 

 prepared by a process elsewhere explained, which conserves the 

 surface features with great accuracy. They evince an interesting 

 lack of stability in the development of the ornament. Thus figure 4 

 has a more primitive aspect than figures 2 and 5, while figure 5 

 though representing a smaller shell shows its individual progression 

 in its fine ornament, broader whorls and narrow umbilicus. Figure 3 

 shows the shell (fig. 2) from the rear, illustrates its lateral compression 

 and obscure carination. x 5. 



From the calcareous concretionary masses in the shales on Big 

 Sister creek, Erie county. 



Manticockkas riiynchostoma, sp. nov. 



(See Plate V.) 



Figures 6. 7, 8, 9. Young shells illustrating the early variations in orna- 

 mentation and the early attainment of a smooth surface. In these 

 specimens the protoconch and first volution are not so clearly defined 

 as to render their appearance here quite dependable, x 5. 



Figure 10. An older shell, x 3, in which the surface of the final whorl bears 

 onlv low bands while the umbilicus shows the earlier ornament. 



Figures 11 and 12. A still later growth phase with the ornament of the early 

 whorls exposed in the umbilicus. Figure 11 shows the great width 

 of the shell at its aperture, x 3. 



All of these early phases are from gutta-percha squeezes. 



Figure 13. The ventral side of the fifth whorl, natural size; showing the 

 slight lateral compression at this stage. 



The specimens of this species are from Big Sister creek, Erie 

 county. 



