630 



MLSS JAKE DONAID 0~N CAEUONIFIEODS 



There is only one specimen in the Museum of Practical Geology ; 

 its length is 10 millim. 



The only shell which this resembles is Turritellat sulcifera, Portl., 

 from which it differs by the form of the band, which is formed of 

 only two keels in T. sulcifera, and the space above the band is 

 greater and slopes more gradually than in that species. 



Locality. Wark, Northumberland. 



Formation. In beds on about the same horizon as the top of the 

 Mountain Limestone and the base of the Yoredales. 



Ttjrritella? sulcifera, Portl. (PI. XXIV. fig. 12.) 



Turritellat sulcifera, J. E. Portlock, 1843, 'Geol. Eep. London- 

 derry,' p. 420, pi. xxxi. fig. 11. 



A minute shell in the Museum of Practical Geology is considered, 

 but not without doubt, to be the specimen figured and described by 

 Gen. Portlock. He describes it as a " minute shell, having ten 

 whorls in less than one third of an inch ; it is narrow and 

 elongated, and has its whorls marked by spiral sulci, bounded by 

 strong spiral ridges, of which there are four on each whorl." His 

 figure is too imperfect to be of any assistance in the way of 

 identification ; but the specimen in the Museum agrees with the 

 description, with the exception that there is a fifth keel on the 

 lower whorls, where it appears just above the suture, and on the 

 uppermost whorls it is hidden below the suture. The apex is 

 broken, but this may have been done since Gen. Portlock's 

 description was written. Thus only seven whorls remain. Of the 

 five keels with which the whorls are ornamented the central and 

 that next above are the strongest, the uppermost is the slightest, 

 and the space below the uppermost keel is the widest. This shell 

 bears a strong resemblance in its characteristics to species of the 

 genus Murchisonia, but as neither the mouth nor the lines of 

 growth are preserved, it cannot with certainty be referred to this 

 genus. Should it be a Murcliisonia, the sinus probably lies between 

 the strongest keels. I have seen no shell resembling this species in 

 the Irish collections in Dublin ; and this is the only specimen I 

 know of that comes near to Gen, Portlock's description. Length of 

 the seven whorls 5 millim., width of the penultimate whorl 

 under 2 millim. 



Locality. Cullion, co. Deny. 



Formation. Shales in the Lower Limestone. This is probably 

 about the same horizon as the lower part of the Mountain 

 Limestone. 



Note. — In concluding this paper I must acknowledge how greatly 

 I am indebted to Prof. Hughes, Prof. Prestwich, Mr. Etheridge, 

 Mr. E. T. Newton, Prof. Schliiter, Dr. Purves, and others, for afford- 

 ing me every facility in studying the collections in the different 

 museums with which they are connected. The Rev. G. Crewdson 

 has also kindly lent me specimens from the Kendal Museum. 

 I am also under great obligations to Mr. Goodchild for revising 

 these notes and assisting me in many ways. 



