G. C. Crick — Cephalopods from the Tyrol. 443 



Fig. 8. The thinnest possible section to make is shown in this figure, magnified 

 75 diameters, exhibiting the extensive individualization of the glass into 

 opaque microliths. The leucite microliths are represented by spots of 

 imperfectly transmitted light where the crystal grains reach both sides of 

 the slice, but are partially overlapped by augite and magnetite all around. - 



Diagram, p. 436. 



A Shells of contraction. 



B Neutral zone or zone of neither contraction nor compression. 



C Dry shells of compression. 



D Aquiferous shells of compression. 



E Fissure between shells of maximum cooling and contraction filled by lique- 

 faction of the edges of these shells by diminished pressure. 



F Same, but in the shells of less cooling and contraction. 



G Fissure extending up between two areas of compression and islands of 

 contraction, but not reaching the aquiferous shells. 



H The same, but reaching into the aquiferous rocks. 



I The same, but having reached aquiferous shells has been enabled to extend 

 upwards by explosive action into a laccolite and sill in one case and 

 directly to a volcano in the other. 



L Laccolite and sill exposed by erosion at M. 



N Volcano supplied from uncooled part of laccolite, aquiferous rocks, aud from 

 rift I. 



Volcano supplied from rift I and aquiferous rocks around top of same. 



P Portion of globe undergoing practically no cooling. 



E, Area of ineffective compression or retraction and depression. 



S Area of ineffective contraction and of low pressure. 



II. — Note on Two Cephalopods collected by Dr. A. P. Young, 

 F.G.S., on the Tarntalek Kopfe, in Tteol.- 

 By G. C. Crick, Assoc. R.S.M., F.G.S., British Museum (Natural History). 

 (PLATE XXVI.) 

 rpHE two Cephalopods — an Ammonoid and a Belemnoid — referred to 

 J_ in the present note were obtained in the summer of 1907 by 

 Dr. A. P. Young from the Tarntaler Kopfe, an isolated mountain-mass 

 in Tyrol, to the north of the Tuxer Alps, and about 20 kilometres 

 south-east of Innsbruck. The Ammonoid was found " at a height of 

 nearly 2500 metres above sea-level, on the surface of a scree-cone 

 which has accumulated under the high hanging valley known as the 

 Lower Tarntal", and the Belemnoid was found "somewhat lower on 

 the slope of the same cone". They are the fossils referred to by 

 Dr. A. P. Young on p. 342 of his paper on the Structure and 

 Physiography of the Tarntal Mass, published in the August number 

 of this Magazine (pp. 339-346), where a photograph of the scree-cone is 

 given (PI. XVII, Fig. 5), and now form part of the National Collection. 

 The Ammonoid ^ and its impression are displayed on the weathered 

 surfaces of two plates of grey limestone that were found within 

 2 feet of one another. Since the impression does not supplement the 

 details exhibited by the fossil itself, no mention is made of it in the 

 following description. The specimen (PI. XXVI, Fig. 1) has been 

 not only crushed, but so greatly distorted during fossilization that its 



1 Had this specimen been chosen from the top of the essential ejecta of Phase III 

 the thinnest section capable of being cut would have been opaque. It was taken, 

 therefore, from a transition stratum (see p. 440). 



- Published by permission of the Trustees of the British Museum. 



3 British Museum (Natural History), register number C. 12113. 



