SPECIES OF CARBON-IFEEOUS MFECHISONIA.. 569 



Mtjechisonia (Hypeegonia) penton-ensis, sp. nov. (PI. XYI. figs. 

 10-12.) 



? Turritella 2 sulcifera, J. E. Portlock, 1843, ' Geol. Rep. London- 

 derry,' p. 420, pi. xxxi. fig. 11 ; H. G. Bronn, 1848, ' Index Pal.' 

 p. 1338. 



Orthonema quinquecarinata, De Kon., ' IN^otes on some Carb. 

 Gasteropoda from Penton and elsewhere,' Trans. Camberl. & West- 

 morl. Assoc. No. ix. (1883-1884) p. 135, fig. 6. 



IS^on Murchisonia quinquecarinata, De Kon., 1883, ' Paune du Calc. 

 Carb. de la Belgique,' vol. viii. pt. 4, p. 23, pi. xxxi v. figs. 14-16. 



? Turritella '^ suleifera, J. Donald, 1887, ' Notes upon some Carb. 

 Species oi Murchisonia in our Public Museums,' Quart. Journ. Geol. 

 Soc. vol. xliii. p. 630, pi. xxiv. fig. 12 ; K. Etheridge, 1888, 'Poss. of 

 Brit. Islands,' vol. i. Pal. p. 308. 



Shell elongated, tnrreted, composed of about twelve angular 

 whorls. Sinual band situated near the middle of the whorl, bounded 

 by two strong keels. Ornamentation consisting above the band of 

 one keel placed near the suture, below the band of three or four 

 keels on the body- whorl, only two of these being visible on the 

 upper whorls. These keels are not so strong as those limiting the 

 band, the uppermost being generally the slightest of all, but occa- 

 sionally the two next below the band are less developed. The 

 widest space is that above the band, the spaces below being about 

 equal. Lines of growth fine and rather irregular in strength, 

 curving backwards to the band above and forwards again below, 

 somewhat indistinct on the band itself. Mouth longer than wide. 

 Columella simple. Base of the shell slightly produced. 



In a previous paper I erroneously referred this shell to the 

 genus Orthonema.^ The examination of a large number of specimens 

 both in my own and Mr. Young's collections, and especially t^ie 

 discovery of a well-preserved specimen upon which the lines of 

 growth are very distinctly seen, have convinced me that this shell 

 should be referred to Murchisonia instead of Orthonema. Many 

 shells from the same beds have fines coming straight down the 

 whorls which appear to be lines of growth, though they are not 

 really so, but merely result from the substance and manner in which 

 the shells are preserved. This is the case with an easily determined 

 species of PUurotomaria, some specimens of which exhibit these 

 straight lines, while the best preserved show the true lines of 

 growth. I also doubt the identification of the species under dis- 

 cussion with M. quinquecarinata, De Kon, ; for I have lately com- 

 pared some of my specimens with De Koninck's type-form at Brussels, 

 and I consider the difference in characteristics such as to lead to 

 their separation into two distinct species. That of De Koninck 

 has a smaller spiral angle, there is a single strong keel on the 

 angle of the whorl with two finer keels above and two or three 

 below ; also the angle is higher up the whorl, and the spaces between 

 the keels are about equal in width. My specimens more nearly 

 agree with seven unnamed shells on Tab. 933 in the Brussels Museum 



^ ' jS^otes on some Carb. Gasteropoda from PentoD and elsewhere,' Trans. 

 Cumb. & WesLm. Assoc. JSo. ix. (1883-84) p. 135, fig. 6. 



