James Geikie — On the Age of the Crofthead Deposits. 53 



ring tlio single vortebra (Figs. 1-3, Plate III,) to the same species 

 as those represented by Fig. 5. 



If no other indications of an enaliosaurian reptile had been 

 obtained from the Triassic (?) beds of Nelson Province, or from the 

 Waipara beds or boulders, the part of a limb-bone — I believe femur 

 — sketched by Dr. Hector, and of w^hich a reduced view is given at 

 Fig. 4 and 4a — would have sufficed. 



It shows the hemisphcroid articular head, coarsely pitted by the 

 characteristic circular depressions, with slightly raised margins. 

 The degi'ee of contraction of the shaft to the broken and the indi- 

 cated retention, so far, of a subcylindrical shape of shaft, are incom- 

 patible with any known modification of an Ichthyosaurian humerus 

 or femur. These are more angular, and transversely oblong at the 

 proximal end, and more rapidly compressed and expanded towards 

 the distant one in the fish-like sea-lizard. The fragment of limb- 

 bone, in the Museum at Wellington, is plainly plesio- or plio-saurian, 

 and most probably part of the same species, if not individual, as 

 the trunk sketched in Fig. 5. The long diameter of the head of 

 the bone is 3 inches, 6 lines ; the short diameter is 3 inches. The 

 peripheral contour is flatter or less convex on one side than the 

 other, as it is in the same part of the femur oi Pliosaurus portlandicus 

 (Monograph, in the volume for 1869, of the PalEsontographical 

 Society, tab. iv., fig. 3), in which the small crateriform pits of the 

 articular surface are shown ; but this character is common to Plio- 

 and Plesio -saur us. 



Other genera of Mesozoic saurians are suggested by the "List" 

 drawn up by my friend, the explorer of this dangerous but richly- 

 stored locality : but the difficulty of precise determination fromi 

 outline-sketches, even as to whether an obviously cup-and-ball 

 vertebra be " pro-" or " opistho-coelian,"' decides one to wait, for the 

 present. 



PLATE III. 

 Plesiosaurus JToodti, Owen. 



Fig. 1. Ciervical vertebra, end view. \ 

 „ 2. „ „ side view. S Half nat. size. 



„ 3k „ „ under view, f 



Plesiosaurus crassicosiaius, Ow€ir. 



„ 4. Proximal part of femur; ) ^ ..i.- j i. • 

 ,; 4«. Articular end of femur. jOiie-third nat. size. 



„ 6. Trunk- ribs and vertebrae from base of neck, one-sixth nat. size. 



II. — On the Age of the Stratified Deposits, with Mammalian 

 Eemains at Crofthead, neah Glasgow. 



By James Geikie, District Surveyor of the Geological Survey of Scotland. 



(With Two "Woodcuts.) 



IN the G-EOLOGiCAL Magazine for September, 1868, I described 

 a section of Drift deposits which had been exposed in the 

 cutting of the " Kilmarnock and Crofthead Extension Railway." If 

 the reader refers to that paper he will find it stated that the Lower 



