Weller — Kinderhook Faunal Studies. 39 



they are new species ; therefore the specimens will simply be 

 referred to their proper genera, and identified specifically as 

 well as possible, with such descriptions and illustrations as 

 can be made, without attempting to found any new species. 



TrOPIDODISCUS CYRTOLITE8 (Hall). 



PL r.f. S-9. 



Shell sublenticular, umbilicate, the periphery angular. 

 The sides of the outer whorl converging with a slightly con- 

 vex outline from near the umbilicus nearly to the prominent 

 angular periphery where the shell is slightly compressed ; 

 rather abruptly curved inward to the umbilicus. The aper- 

 ture subcordate, the margin with a broad and deep but not 

 sharply defined sinus at the dorsal angle. Surface covered 

 with very fine but conspicuous costae parallel with the margin 

 of the aperture, and by much less distinct revolving lines, 

 which together give to the shell under a lens, a very beautiful 

 cancellated appearance. 



Remarks. This species belongs to a group of the Beller- 

 ophontidae with B. curvilincatus Conrad, as the type, for which 

 Meek * proposed the name Tropidiscus, but a little later 

 changed it to Tropidodiscus.'\ DeKoninck| pointed out that 

 the name Tropidiscus was already preoccupied in 1850 by 

 Stein for a genus of fresh water snails, and proposed to sub- 

 stitute Tropidocyclus instead of using Meek's second name 

 Tropidodiscus. Since there seems to be nothing against the 

 name Tropidodiscus it is adopted here instead of DeKoninck's 

 much later name Tropidocyclus. 



The species is represented by several specimens from North- 

 view, all of which are fragmentary, although one of them 

 shows the margin of the aperture in great perfection. The 

 species was originally described from internal casts from the 

 " goniatite beds " at Rockford, Indiana, and in the typical 

 specimens the delicate surface markings seen in the North- 

 view specimens were not preserved. The species has been 

 found, however, in some of the Waverly beds of Ohio and 



♦ Proc. Chicago Acad. Sci. 1 : 9. (March, 1866). 



t Qeol. Surv. 111. 2: 160. (1866). 



t Faun, du Calc. Carb. de la Belg. pt. 4: 16C. (1883). 



