Vol. 51.] MUECHISONIA AND ITS ALLIES. 225 



Mr. J. Thomson, Glasgow, possesses one specimen. It consists of 

 twelve whorls ; both apex and base are broken. Length = 8-1- 

 millim. ; width of penultimate whorl = about 2g millim. 



Locality. Dairy. 



Formation. Upper Limestone Series (d s ). 



Murchisonia Thomsoni, sp. nov. (PI. IX. fig. 1.) 



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

 "Whorls angular about the middle, gradually increasing. On the 

 angle there are two keels placed close together with only a narrow 

 groove between ; this probably represents the sinual band. The 

 ornamentation consists of three keels below the band, and two 

 above, the former placed at equal distances from each other and the 

 latter having a wide space between them, one being immediately 

 below the suture and the other a little above the band ; there is an 

 additional keel on the body-whorl. Lines of growth not preserved. 

 Sutures oblique. Mouth imperfectly known. 



The very narrow sinual band distinguishes this from all other 

 Carboniferous species. 



A single specimen of this species is in the collection of Mr. James 

 Thomson. Only five whorls are preserved. Length = 7| millim. ; 

 width = 2% millim. 



Locality. Craigenglen. 



Formation. Lower Limestone Series (d 3 ). 



MtTItCHISONIA YoTTNGIANA, sp. nOV. (PI. VIII. figS. 10, 13.) 



Shell very elongated, turriculated, composed of more than sixteen 

 whorls. Apex acute. Whorls almost convex, but slightly angular. 

 The lower half of the whorl is ornamented by four keels of about the 

 same strength and separated by nearly equal spaces ; above, there 

 is a much slighter keel just below the suture. Lines of growth not 

 visible. Sinual band probably situated on the most prominent part 

 of the whorl, between the two uppermost of the four keels. Base 

 flattened, without additional keels. Mouth oval. Columella simple, 

 nearly straight. 



This shell most resembles Turritella (?) sulcifera, Portl., 1 but the 

 only known specimen of that species is too small and imperfect for 

 positive identification. It also bears some similarity to M. penton- 

 cnsis, Don., 2 but it is more elongated, the whorls are more convex, 

 the keels more nearly equal in strength, and the spaces separating 

 them of about the same width ; there are no additional keels on the 

 body-whorl, and the base is somewhat flattened instead of being 

 produced. 



A specimen in the collection of Mr. J. Smith (PI. VIII. figs. 13, 

 13 a) consists of fifteen whorls; the apex is entire, but the base is 

 broken. The nucleus is convex and smooth, and probably consists 



' Notes upon some Carb. Sp. of Murchisonia in our Public Museums,' Quart. 

 Journ. Geol. Soc. vol. xliii. (1887) p. 630, pi. xxiv. fig. 12. 



- ' Notes on some New and Little-known Species of Carboniferous Murchisonia, 

 Quart. Journ. Geol. Soc. vol. xlviii. (1892) p. 569, pi. xvi. figs. 10-12. 



