Yol. 51.] HTTKCHISOHTA AND ITS ALIIES. 233 



the lines of growth, with the exception of one or two upper ones 

 on the higher whorls which are stronger and rendered moniliform 

 by the lines of growth ; this feature becomes fainter as the whorls 

 increase. Lines of growth distinct and sharp, curving backwards 

 to the band above and forwards below ; on the band itself they are 

 so strong as to form imbricated lamellae, and the keel on the body- 

 whorl is crenulated where they cross. Base more or less flattened. 

 Mouth polygonal. Columella simple. No umbilicus. Test mode- 

 rately thin. 



In the Museum of Practical Geology, London, there are seven 

 specimens marked Pleurotomaria tahulata which agree with that 

 species as figured and described by Conrad, except that the spiral 

 lines on the base are not rendered moniliform by the crossing of 

 the lines of growth. On some of these individuals the sinual band is 

 the same as on the type, being a strong convex keel ; on others there 

 is a shallow groove on each side of a sharp and less strongly de- 

 veloped keel. Murchisonia angulata, Portl., appears to be identical 

 with Conrad's species. It has the sinual band formed in the latter 

 way ; the central keel is perhaps rather sharper, and the lateral 

 grooves more marked, than on any of the other specimens ; also the 

 spiral angle is slightly less. But the different individuals vary some- 

 what, therefore it does not seem necessary to recognize it as a 

 distinct variety. The surface of the higher whorls is not well 

 preserved, but a small portion of the penultimate whorl shows 

 traces of the crenulations on the upper part. The Murchisonia 

 angulata of Portlock is quite distinct from either of the shells so 

 named by Phillips in the ' Geology of Yorkshire,' this having a 

 greater spiral angle and the ornamentation and form of the band 

 being different. De Koninck identifies it with Worthenia Waageni, 1 

 from which it differs in the band being nearer the middle of the 

 whorl, in the space between it and the lower keel being wider, and 

 in not possessing an umbilical chink. 



Portlock's type (PI. X. figs. 2, 2 a), which is in the Museum of 

 Practical Geology, has the apex broken and only four whorls 

 remain ; these have a length of 30 millim., and a width of about 

 20 millim. 



Locality. Aghalurcher, Tyrone. 



Formation. Carboniferous Limestone Shale (d 3 ). Probably the 

 middle division (Calp). 



The specimen figured (PI. X. figs. 4, 4 a, b) is 33 millim. in length 

 and 28 millim. in width. 



Locality. Hammerton Hall, Slaidburn (near Clitheroe), Lanes. 



Formation. Bottom of Yoredale Shales (of). 



In the Woodwardian Museum, Cambridge, there is a single speci- 

 men of this species mounted on the same tablet as M. kendalensis, 

 M'Coy. 



Locality. Kendal. 



Formation. Mountain Limestone (d 2 ). 



1 Ann. Mus. Eoy. Hist. Nat. Belgique, ' Faune du Calc. Carb. de la Belgique,' 

 vol. viii. (1883) pt. iv. p. 67, pi. xviii. figs. 32, 34, & pi. xxxii. bis, figs. 32-35. 



