CALL] NOTES ON SOME UPPER CRETACEOUS VOEUTlDiE 1 5 



Shell with one moderately elevated plait in the penultimate whorl, 

 obsolete at the aperture ; fourteen to sixteen straight axial ribs, ex- 

 tending from shoulder to suture, with wider interspaces ; behind the 

 suture each rib has three obscure nodulations ; suture appressed and 

 swollen by a deposit of callus in the wake of the posterior sinus of 

 the aperture ; sinus situated at the suture, in the adult wide and deep ; 

 whorl in front of the suture constricted, carrying strong lines of 

 growth and obsolete distant spiral cords, which also exist over the 

 body ; where each cord terminates at the outer lip appears a small 

 projecting denticle; outer lip in the adult somewhat expanded; the 

 whole shell at maturity covered by a coating of enamel which still 

 further obscures the sculpture and sutures ; whorls about five, the 

 nucleus shelly, defective. Lon. of shell, 162; of aperture, no; diam., 

 58 mm. 1 



Ripley formation of upper Cretaceous at Ripley, Miss. ; the same 

 horizon at Eufaula, Alabama ; Bullock's Mill, near Dumas, Miss. 

 (20,576) ; and near Mt. Olivet Church, Union county, Miss. 

 (20.534) ; U. S. Nat. Mus. and Acad. Nat. Sci., Philadelphia. 



The plait on the pillar in the fully adult shell becomes obsolete in 

 the vicinity of the aperture and is invisible from in front. In the 

 earlier whorls it is strong, lying in front of a shallow channel on the 

 pillar ; the posterior border of this channel, in the early stages of the 

 shell, forms a second fairly well-marked plait. The substance of the 

 shell as preserved is chalky white with a yellow-brown coating of 

 enamel. 



VOLUTOMORPHA RETIFERA Dall, n. sp. 



(Figures 2, 3) 



Shell with one evident plait in the adult, two in the early stages, 

 lagging behind the aperture and hardly visible from in front ; penul- 

 timate whorl with eighteen to twenty-one rounded ribs, most prom- 

 inent at the shoulder, obsolete on the last half of the last whorl, but 

 earlier extending well toward the base, with subequal interspaces; 

 posterior sinus of the aperture deep, narrow, in the adult recurved 

 (see figure 3), leaving a prominent ridge of callus in front of and 

 close to the suture, in front of which the whorl is excavated, mark- 

 edly so in the earlier whorls, and spirally obsoletely striated ; the rest 

 of the surface with about twenty-two spiral, strap-like ridges, very 



1 Conrad's original figure, though characteristic, was taken from a crushed 

 specimen which is abnormally wide. 



