100 THE LIAS AMMONITES. 



containing flattened concretionary nodules, which are rich in phosphates, the decomposi- 

 tion of which contributes to the fertility of the soil. Silicate of iron in small, rounded, 

 highly polished, often hollow grains, is sometimes so abundant as to give almost an 

 oolitic structure to the rock. 



At Adderbury and at King's Sutton extensive workings for ironstone are now 

 carried on in these beds, which are the correlative series in the midland districts of the 

 great ironstone beds of Yorkshire, and are estimated to yield from 18 to 24 per cent, of 

 iron. 



Mr. Beesley has collected eighty species of Mollusca from the Spinaius-heds ; and in 

 this list are included, with Amalf/ieus spinaius and Amal. margaritatus, two Ammonites 

 which belong to the Upper Lias. It would appear that here, as in other localities, it is 

 extremely difficult to separate certain forms from each other along the confine lines of 

 these zones, and hence we learn how the Spinatics- and Margaritatiis-hedi?, have been 

 united and considered as one by most British geologists. 



The Middle Lias zones above the Jamesoni-heds are exposed in the Island of Raasay, 

 along the stream-courses on the Hallaig Moor ; and, according to Professor Tate,^ form a 

 grand section on the east side of the island, displaying a gradual passage from argillaceous 

 sediments into the calcareo-arenaceous rocks which constitute so striking a feature in the 

 lithology of the Middle Lias of this area. A section of 1 50 feet shows the following beds : 



I. Spinatus-heds : 1, yellow calciferous sandstone with ferruginous nodules. 



II. Margaritatus-heds consisting of, 2, fissile sandstone ; 3, shelly, ferruginous 

 sandstone ; 4, marly sandstone ; 5, grey marls ; 6, greenish-yellow sandstone, with shaly 

 partings ; 7, yellow sandstone ; 8, greenish marly sand beds. 



III. IIe7ile?/i-hed& : 9, greenish-yellow calcareous sandstone; 10, greenish calcareous 

 sandstone, with indurated tops. 



In the cliff section on the east coast of Skye these three zones are repeated with 

 similar petrological conditions ; and from the JIenie?/i-heds the following fossils were 

 collected by Messrs. Tate and Bryce, near Portree, Isle of Skye. 



Fossils from the Henleyi-zone, Skye. 



Aegoceras Henleyi, Sow. 



— Davcei, Sow. 



— striatum, Reinecke. 

 Pecten sequivalvis, Sow. 



— liasinus, Nyst. 

 Avicula novemcostse. Brown. 

 Limea acuticosta, Miinst. 

 Unicardiutn Jan the, iVOrh. 

 Protocardiuni truncatum, Phil. 

 Pholadomya ambigua, Sow. 

 — decorata, Ziet. 



Pleuromya ovata, Hum. 



Mytilus scalprum, Sow. 

 Area Stricklandi, Tate. 

 Cypricardia cucuUata, Goldf. 

 Inoceramus ventricosus, Sow. 

 Gryplisea cymbium, Lamlc. 



— obliqua. Sow. 

 Hippopodium ponderosuin, Sow. 

 Pinna folium, Youny ^ Bird, 

 Cuculisea Munsteri, Ziet. 

 Rhyncbonella tetraedra. Sow. 

 — variabilis, Sow. 



' 'Quart. Journ. Geol. Soc.,' p. 343, vol. xxix, 1873. 



