500 J. W. Gregory and Ethel Gurrie — 



apart from volatile agents — is limited to silica. Where the diopside 

 masses have been engulfed as inclusions in the igneous gneiss, the 

 rock is traversed by felspathic veins derived from the fluid magma. 

 The writer wishes to record his indebtedness to Dr. Harker, F.R.S., 

 for encouragement and critical discussion during the progress of 

 these studies. 



EXPLANATION OF PLATES IX AND XL 

 Plate IX. 

 Fig. 1. — Forsterite Marble, Sleaford Bay. The minerals shown are calcite 

 (turbid), dolomite (limpid). The dark grains are forsterite, showing 010 

 cleavages. Near the centre is a basal section of edenite. Magn. 28 diameters. 

 Fig. 2 — -Forsterite Marble, Sleaford Bay. Constituents : forsterite, with 

 serpentinous decomposition, calcite, dolomite. Twinning lamellae in 

 dolomite are seen in relation to the rhombohedral cleavages, in the clear 

 grain below on the left, Magn. 28 diameters. 



Plate XI. 



Fig. 1 — Diopside Rock, Sleaford Bay. The dark bands are diopside. a.nd 

 the white are quartz veins. The reticulation of the latter is clearly marked. 



Fig, 2. — Diopside-Microcline Rock. The clear central area is microcline. In 

 the upper half of the section are basal sections of scapolite showing 110 

 cleavages at right angles, and diopside. Magn. 28 diameters. 



Echinoidea from Western Persia. 



By J. W. Gregory and Ethel Currie, Geological Department, 

 University, Glasgow. 



(PLATE XII.) 



rriHE Geological Department of Glasgow University has recently 

 -■- received from Dr. W. R. Smellie and Mr. J. V. Harrison some 

 fossils collected by them which throw further light on the age of the 

 limestones of the Persian arc at the north-western end of Luristan, 

 about 100 miles north-east of Baghdad. The locality, Gilan, is on 

 a tributary of the Diala, about 30 miles south-east of Kasr-i-Shirin, 

 a well-known station on the main road from Baghdad to Teheran. 

 The geology of this part of the Persian frontier has been investigated 

 by J. de Morgan (Miss. Sci. Perse, vol. iii, pt. i, Etud. Geol., 1905, 

 pp. 71-112), who has given a geological map (ibid., pi. xix) of an 

 area about 60 miles south-east of Gilan. De Morgan has identified 

 there a folded series of Cretaceous and Eocene limestones, with 

 lacustrine and gypsiferous Miocene beds. The locality at which the 

 fossils were collected by Messrs. Smellie and Harrison is in line with 

 the strike of the rocks in the area of de Morgan's map. 



Dr. Smellie's collection was made at Iman-Hasan, near Gilan, 

 from a limestone on the summit of an anticlinal inlier, which is 

 unconformably covered by limestones referred to the Eocene. The 

 fossils include various echinoids, molluscs, brachiopods, corals, 

 and bryozoa. The echinoids give the best evidence of correlation. 

 His collection includes the following echinoids : — 



