368 Mr. Horner 07i the Geology of the 



brownish yellow or cream colour, which is of different thicknesses, 

 in some places extending so far into the interior of the stratum that 

 the blue colour is nearly obliterated. I very rarely found organic re- 

 mains in these beds. 



§ "i^. The other variety of the limestone is of a much darker 

 colour, but is most particularly distinguished by the strong fetid 

 smell it gives out when struck by the hammer, and when it is burn- 

 ing in the kilns. It is always in thicker strata than the other variety 

 and abounds in organic remains, it is also very much penetrated by 

 pyrites in many places. These fetid strata have much less the property 

 of setting under water, and are best adapted for agricultural pur- 

 poses, for which the other are very unfit. Th« quarriers on the 

 spot call the first blue lyas and building lime, the other black lyas and 

 ground lime. They informed me that the building lime always lies 

 above the ground lime, and in a quarry in the parish of St. Decu- 

 man's I saw a section where the upper strata were pointed out to 

 me by the workmen as the best building lime, and they find the 

 strata become less adapted for that purpose the lower they go. I 

 found the middle beds slightly fetid, and the lowest more so and in- 

 creasing in thickness. 



§ ^Q. The fossils which are very numerous in the lyas series In 

 most places, appear to be less abundant here. The cornu ammonis 

 is the most common, and I found it several times above 18 inches 

 in diameter. It frequently occurs in a flattened compressed state 

 with the beautiful iridescence of the nacre preserved ; a variety which 

 Mr, Townsend considers peculiar to the lyas of this coast.* The fol- 

 lowing are the few organic remains I had an opportunity of collecting; 



Remains of a very finely striated Pecten or Lima. 



* Character of Moses, p. 278. I\Ir. Townsend is mistaken in supposing that the 

 Pentacrinite is not found in the lyas of Watchet. 



