224 MISS J. DONALD ON THE GENUS [May 1 895, 



Mdrchtsonia Marei, sp. nov. (PI. IX. fig. 2.) 



Shell elongated, turriculated, composed of more than nine whorls. 

 Whorls increasing gradually, slightly angular, rather flattened 

 above, more convex below. Sinual band situated near or a little 

 above the middle of the whorl, narrow, bounded on each side by a 

 moderately strong keel. Ornamentation below the band consisting 

 of three slighter keels, with sometimes a thread between each of 

 them ; above the band there are from one to three threads, the 

 uppermost appearing just below the suture, another being about 

 halfway between it and the band, and there is sometimes a third 

 between that and the band. Lines of growth curving backwards 

 to the band above and forwards below. Sutures deep. Mouth 

 unknown. 



The species which this most resembles is M. elongata, 1 Portl., from 

 which it differs in having a smaller spiral angle, more convex 

 whorls, band situated higher up the whorls, and more numerous 

 keels below the band. It is also somewhat like Aclisina striatuld, 

 De Kon., 2 but the lines of growth appear to indicate a true sinus in 

 the outer lip, the upper part of the whorl is more flattened, and the 

 spiral threads are less numerous. 



Some external casts of this shell have been discovered by 

 Mr. Marr. The figure is drawn from a wax impression. None of 

 the individuals are entire. Length of that figured (PI. IX. fig. 2) 

 =22| millim. ; width = 10 millim. 



Locality. Shap. 



Formation. Carboniferous Limestone (d 2 ). 



Mtjechtsonia daleyensis, sp. nov. (PI. IX. fig. 3.) 



Shell elongated, turriculated, composed of more than twelve 

 whorls. Whorls somewhat convex, slightly angular about the 

 middle. Upon the angle there are three strong threads of nearly 

 equal strength, placed close together, which probably represent the 

 sinual band. Below this band there are three fine threads, then a 

 space, which is succeeded by a very strong thread appearing just 

 above the suture. Upper half of the whorls smooth. No lines of 

 growth preserved. Sutures not much inclined. Mouth unknown. 



This species strongly resembles members of the genus Aclisina, 

 De Kon., in the convexity of the whorls and the ornamentation. In 

 spite of the mouth and lines of growth not being preserved, I refer 

 it provisionally to the genus Murcliisonia — on account of the three 

 threads placed close together being suggestive of a sinual band. 

 Also it is somewhat like M. subtilistriata, Don., 3 from which species 

 it may be distinguished by its less angular whorls, band formed of 

 three threads instead of one strong keel, and the ornamentation 

 being rather different. 



1 ' Eep. on Geol. of Londonderry,' 1843, p. 569, pi. xxxviii. fig. 10a, b. 



2 Ann. Mus. Koy. Hist. Nat. Belgiqne, ' Faune du Calc. Carb. de la Belgique,' 

 vol. vi. (1881) pt. iii. p. 86, pi. ix. figs. 57, 58 ; vol. viii. (1883) pt. iv. pi. xxxiii. 

 figs. 41, 42. 



3 ' Descr. of some New Sp. of Carb. Gasteropoda,' Quart. Journ. Geol. Soc. 

 vol. xlv. (1889) p. 623, pi. xx. figs. 7, 8. 



