FOSSILS OF THE SILURIAN AND DEVONIAN ROCKS. 175 



extending into the umbilicus. The chief external characters of this genus 

 being the sharply elevated, even, thread-like, concentric striae traversing the 

 volutions above and below, a distinct columellar lip, and an umbilicate axis. 



Callonema bellatula. HALL. 



Plato XX., figures 4, 5, 6 and 7. 



Laxonema bellatula, Hall. 14th Rep. N. Y. St. Cab., p. 1041861. 

 Isonema bellatula, Meek. Proc. Acad. Nat. Sci. Phil., p. 252 1865. 

 Isonema bellatula, Meek. Geol. Surv. of 111., Vol. 3, p. 4431868. 

 Isonema bellatula, H. and W. 27th Regent's Rep., pi. 131875. 

 Isonema bellatula, Hall. Illust. of Dev. Foss. Gaster., pi. 14 1876. 

 CaOanema bellatula, Hall. Pal. N. Y, Vol. 5, pt. 2, p. 511879. 



Shell sub-ovoid-conical ; spire elevated and rapidly expanding below. Volu- 

 tions about six or seven, the upper ones minute, and somewhat gradually ex- 

 panding to the third or fourth whorl, and more rapidly below, the last one being 

 very ventricose, regularly rounded or obtusely subangular towards the base. 

 Aperture apparently transverse ; the specimen before me, and represented by 

 figure 7, is perfect, with the exception of the peristome, of which the outer lip 

 is missing ; I am, therefore, unable to state the exact form of the aperture ; col- 

 umellar lip thickened, spreading above and extended anteriorly. In my speci- 

 men the umbilicus is partly open, and partly closed by the columellar lip. 



Surface is covered by regular, even, sharply elevated striae, with about equal 

 interspaces, which are slightly turned backwards from the suture, and gently 

 curved to the base of the volution, and on the last one curving over the per- 

 iphery with equal strength ; a portion becoming obsolete and others coalescing 

 and becoming stronger as they enter the umbilical depression. Some specimens 

 of this species show an obtuse angularity at the base of the last volution, as 

 slightly indicated in figure 6 ; but most shells are regularly rounded and ven- 

 tricose. There is no specific difference between these two forms. This species 

 has a close resemblance to Callonema lichas, with which it may even be identi- 

 cal. 



Formation and Locality. Occurs in the Corniferous limestone at and around the Falls of the Ohio 

 in Kentucky and Indiana, and belongs to the rarer forms. 



Callonema clarki. N. sr. 



Plate XXIV., figures 2, 3, 4 and 5. 



Shell above medium size ; sub-hemispherical ; spire moderately elevated, 

 more or less so in different shells, as shown by the two specimens illustrated, 

 consisting of from three to five volutions. The volutions are regularly increas- 

 ing from apex to aperture, which is sub-circular or subquadrate; they are 

 depressed convex on their upper 



