FOSSILS OF THE SILURIAN AKD DEVONIAN ROCKS. 177 



Genus Loxonema. phniips. 



Lotonema, Phillips. Palaeoz. Fossils 1841. 



Etymology : loxos, oblique); nema, a thread alluding to the oblique thread-like striae. 



Shell spiral, turriculated ; whorls or volutions convex, their upper edges 

 pressed against the next above ; without spiral band ; mouth oblong, attenu- 

 ated above, effused below, with a sigmoidal edge to the right lip ; no umbil- 

 icus (?). 



Surface covered by longitudinal threads, and ridges generally arched. (Geol. 

 Rep. of Londonderry, by J. E. Portlock.) 



Loxonema sinuata is the type of this genus. 



Loxonema hamiltoniae. HALL. 



Plate XXXI., figure 29. 



Loxonema hamUtoniae, Hall. Dcscpt. of New Sp. of Foss. 1861. 

 Loxonema hnmillonine, Hall. 15th Regent's Rep. 1862. 

 Loxonema hanrittoniae, Hall, lllust. of Dev. Foss., pi. 13 1876. 

 Loxonema kamiUoiiiae, Hall. Pal. N. Y., Vol. 5, pt. 2, p. '45 1885. 



Shell elongate, subulate ; volutions moderately convex, numbering from ten 

 to thirteen ; as many as the last number were counted in the largest specimen 

 known. The volutions are gradually increasing in size from the very minute 

 apex to the aperture ; the last one becomes ventricose. Aperture ovate, nar- 

 rowing below, colutnella extended. 



Surface marked by longitudinal, sharp, curving striae, which bend gently 

 backward from the suture, and forward to the base of the volution, having 

 the greatest curve near the middle, those of the last volution curving abruptly 

 backward to the columellar lip. Striae separated by distinctly defined grooves, 

 which are a little wider than the ridges, the striae increasing in distance as the 

 shell grows older. In the specimen figured, the apical volutions are missing ; 

 the draughtsman restored them, but he made the volutions too high, and not 

 enough in number. The height of the figure would have been the natural size 

 of the shell when complete ; it should have shown twelve volutions instead of 

 its present nine. It measures seventeen lines in length, and its body-whorl 

 has a diameter of four lines. This species is associated with L. hydraulica, 

 which it resembles in its surface-markings, but it may be easily distinguished 

 from that shell by the different shape of the volutions and suture. In L. hy- 

 draulica the whorls are very convex, while in L. hamiltoniae they are only 

 moderately curved ; the suture in L. hydraulica is very deep and constricted, 

 that of L. hamiltoniae comparatively very shallow. Besides, the spire in L. 



hamiltoniae is more elongate than that of L. hydraulica. 







Formation and Locality. Occurs in the chert bed which overlies the hydraulic cement rock at the 

 Falls of the Ohio, on the Kentucky shore of the river, and also at Watson's Station, on the Ohio and 

 Mississippi Railroad, in Clark county, Ind. 

 a KOI., suu. 22 



