134 



very distinct, but sufificiently well-marked to be made out with the 

 aid of a magnifier, when a strong light is cast obliquely on the 

 surface of the specimen under examination. The mouth is nearly 

 round, and the columella is slightly thickened. 



This shell bears some resemblance to A. elongata, but the keels 

 are decidedly stronger, as well as less numerous. From Loxonenia 

 polygyra, M'Coy, it differs in its more numerous whorls, and in 

 the keels being placed at unequal distances on. the surface of the 

 whorls. The description given by Professor M'Coy, however, is 

 too brief for satisfactory identification, and I have not seen the 

 type specimen. Both this species and A. elongata, Flem., resemble 

 Tiirritellal stevensana. Meek and Worthen, but each differs from 

 it in having a smaller spiral angle. 



Length, 5^ mm.; width of body whorl, rather more than 

 \\ mm. 



Locality. — Specimens of this shell are fairly abundant at Penton, 

 the most frequent size having nine or ten whorls. Mr. Young has 

 also found this species at Cunninghambaidland, Dairy, in the 

 shales of the Lower Limestone Series ; and at Glencart, Dairy, in 

 the shales of the Upper Limestone Series. 



Horizon. — Lower Carboniferous Series. 



Genus Orthonema. (Meek and Worthen.) 



Shell elongated, of numerous whorls, ornamented with spiral 

 keels crossed by nearly straight lines of growth. Mouth angular 

 above and slightly effuse below; peristome incomplete; lip simple 

 and nearly straight. No umbilicus. 



This genus bears considerable resemblance to Murchisonia ; but 

 the absence of a slit in the outer lip distinguishes it. From 

 Adisina it differs in having less rounded whorls, and the Hues 

 of growth straight instead of curved. Messrs. Meek and Worthen 

 give, as the typical species of the genus, O. salteri, which was 

 described as Eunemal salteri in the Proc. Acad. Nat. Sci. Phil., 

 p. 464, i860, and was figured in the Geol. Siirv. Illinois, Vol. ii., 

 PI. xxxi,, fig. 14, 1866. The type species is from the Upper Coal 

 Measures. 



