SPECIES OF CAEBOlSriFEROUS MFECHISONIA. 565 



the two upper keels ; it is occupied by the sinual band. Lines of 

 growth curving backwards to the band above and forwards again 

 below, arched upon the band itself. Base somewhat produced. 

 Mouth longer than wide. 



Several different forms having been erroneously named M. quadri- 

 carinata, I consider it advisable to give a fuller description and 

 enlarged figure of the type of this species. It is unfortunate that 

 there is only one specimen from the original locality, and that it is 

 embedded in the matrix. Thus we cannot tell what amount of 

 variation in the strength and position of the keels there might be 

 if a large series were available for comparison. Also the exact 

 spiral angle is not seen. The shell is, however, well preserved, and 

 shows traces of the lines of growth. It is quite distinct from the 

 form called M. quadricarinata by De Koninck: the whorls are 

 more angular, the sutures deeper, there is also a difference in both 

 the number and the position of the keels, and the base of the shell 

 is more produced. It bears a great resemblance to M. quinque- 

 carinata^ De Kon. ; but in that species the whorls are higher in 

 proportion to the width, the angle being in the middle or above the 

 middle of the whorl, and three keels being frequently visible below 

 it on the lower whorls ; the spaces between the keels are more 

 nearly equal in width, and the sutures are more oblique. M. quin- 

 quecarinata may, however, prove to be merely a variety having the 

 whorls less closely coiled. 



The type (PI. XVI. figs. 3, 3 a) which is in the Museum of Science 

 and Art, Dublin, is embedded in the matrix, and only nine whorls are 

 visible ; these have a length of 11 millim. Width of portion of 

 body-whorl seen 3 millim. ; height 2| millim. 



Locality and Formation, Upper (Carboniferous) Limestone of 

 Blacklion, Enniskillen. 



In the Woodwardian Museum there are two shells from the 

 Carboniferous Limestone of Derbyshire referred, but with a query, 

 to this species by M'Coy himself ; I also doubt their identity with 

 the Irish specimen. They are, however, so badly preserved that it 

 is difficult to tell what they really are. 



Pour small shells from the Mountain Limestone of Settle appear to 

 belong to this species. Three are in the Woodwardian Museum, and 

 the other is in the York Museum. This last (PI. XVI. figs. 4, 5) is 

 remarkably well-preserved, showing the lines of growth very dis- 

 tinctly, and in the middle of the band there is a fine thread on the 

 two lower whorls. The two keels below the band are about equal 

 in strength instead of the upper being the stronger, as is the case in 

 the type. Eight whorls are preserved, and there would probably 

 be two or three more if the apex were entire. 



Length 8^ millim. ; width of body-whorl 3| millim. ; height 2| 

 millim. 



There is also, from the same locality, a fragment of a larger shell 

 in the Woodwardian Museum which bears a great similarity to this 

 species in the position of the angle and in ornamentation. The 

 space above the angle is not quite so wide, and the dimensions are 



