66 



rather diverging from an imaginary central line towards both 

 the inner and outer surfaces, as shown at fig. 4, and partly 

 in fig. 3. When several of the coats are broken off the ex- 

 posed portions of those remaining have the appearance of 

 trumpet-shaped tubes inserted into one another, as may be 

 seen in figures 2. and 3 : a longitudinal section, that is, in 

 the direction of the axis of the shell, shows fibres perpendi- 

 cular to the surface, as round the aperture in fig. 1 : this 

 structure was first pointed out by Mr. Lonsdale, who had 

 a portion (fig. 4.) polished in which the variation of colour 

 assists in developing the thickness of the layers, A similar 

 structure may be traced, less readily, in Euomphahis. The 

 edge of the mouth has a slight sinus, formed by the project- 

 ing keel that runs round the spire upon the whorls ; it is 

 otherwise even, and is continued over the preceding whorl ; 

 it is placed more perpendicularly than in Euomphalus pen- 

 tangulatus; in old subjects it becomes elliptical and trans- 

 verse. A few obscure furrows may be observed along the 

 whorls, and add somewhat to the rugosity of their upper 

 parts; the base and the umbilicus are particularly smooth. 

 In old shells septa are formed which separate the smaller 

 whorls, as in many other spiral shells, especially in Euom- 

 phalus. 



This appears to be an abundant shell near Kendal ; our 

 figure 3. is taken from a portion of one sent me by the Rev. 

 Mr. — Fisher from that place, and several fine specimens 

 from the same locality are preserved in the University 

 Museum at Cambridge. Fig. 1. is from the best individual 

 in Mr. Gilbertson's collection, at the British Museum ; 

 fig. 2. from Settle in Yorkshire ; and fig. 4. a section made 

 by Mr. Lonsdale of a fragment from Ireland, placed in the 

 cabinet of the Geological Society by the Earl of Ennis- 

 killen. It also occurs in Northumberland and other places 

 in the middle and lower beds of the carboniferous lime- 

 stone. 



Cirrus acutus, tab. 141. f. 1, is distinguished by the form 

 of the upper portion of the whorl. 



