720 J. W. JTTDD ON THE SECONDARY ROCKS OP SCOTLAND. 



The division III. yields a considerable number of fossils, Beleni- 

 nites of several species, B. giganteus, Schloth., and B. aalensis, 

 Yoltz, especially, being particularly abundant ; and with these there 

 occur specimens of Ammonites Humphriesianns, Sow., and of several 

 of its varieties, such as A. Blagdeni, Sow., arid A. coronatus, Ziet. 

 A few other marine fossils, with some plant-remains, also occur at 

 this horizon, which clearly represents the Zone of Ammonites Hum- 

 phriesianus. 



The division IV. is much richer in fossils than any of the higher 

 members of the Lower Oolite, Ammonites Murchisonce, Sow. (first 

 described from a specimen obtained on the coast of Trotternish, near 

 the islet of Holm), is particularly abundant throughout the division ; 

 and with the normal type of this species there occur many of the 

 varietal forms, such as Am. corrugatus, Sow., Am. Iceviusculus, Sow., 

 &c. A number of species of Belemnites also occur with some well- 

 known Inferior-Oolite Lamellibranchiates and Brachiopods. It is 

 clear, from the nature of its fauna, that this division must be assigned 

 to the Zone of Ammonites Murchisonce. 



In the lowest part of the Lower- Oolite series of the Western 

 Highlands I have detected a few fossils which seem to indicate the 

 existence of a representative of the Midford Sand of England, and 

 constitute a transition series into the Upper-Lias beds beneath. The 

 horizon is not by any means well marked, and the very characteristic 

 forms of Ammonites are, so far as I have been able to determine, 

 wholly wanting in it. 



Taken altogether, the Lower-Oolite strata of Skye, which are so 

 well exhibited in their entirety in the fine cliff-sections above Prince 

 Charles's Cave and the Holm Islet, and of which numerous partial 

 exposures occur at the Beal, Scoribreck, and along the coast south- 

 ward from Portree, may with great probability be regarded as repre- 

 senting both the Great and Inferior Oolite. But while it is quite 

 certain that the divisions III. and IY. represent the lower part of the 

 Inferior Oolite, some doubt still exists as to whether the divisions 

 I. and II. should be regarded simply as the upper part of the In- 

 ferior Oolite, or as belonging in part to the Great Oolite also. 



In the island of Raasay the Lower-Oolite beds appear in great 

 force, but are exposed only in a series of vertical cliffs, which are 

 almost everywhere perfectly inaccessible. Prom a comparison of the 

 points at which the several members (which agree very closely in 

 character with the strata already described in Skye) make their ap- 

 pearance, and a knowledge of the heights of certain points in the 

 cliffs, we are able to appreciate how very grand is the development of 

 the Lower-Oolite formation in these fine mural precipices of Raasay. 



The estuarine conditions which prevail in the division II. of the 

 Skye section are equally well marked in the equivalent beds in 

 Raasay, and appear to extend down through a great part of the 

 division TIL ; in this island, indeed, a thin seam of coal has been 

 found in one place at the horizon in question. In this part of the 

 series the strata appear to have even a greater thickness in Raasay 

 than in Skye. The lowest division (IY.), too, appears to exhibit 



