Geological Society of London, 423 



10. ''On Crocodilus icenicus, Seeley, a second and larger Species 

 of Crocodile from the Cambridge Upper Greensand, contained in the 

 Woodwardian Museum of the University of Cambridge." By Harry 

 Govier Seeley, Esq., F.L.S., F.G.S., etc. 



In this paper the author described a cervical and a dorsal vertebra 

 of a new species of Crocodile. The former is probably the last 

 cervical. It is 2^ inches long, and differs from that of existing 

 Crocodiles in the large size of the parapophyses, the distinct anterior 

 notch in the neural arch for the vertebral nerve, and the perfect 

 convexity of the articular ball. The dorsal vertebra is the sixth or 

 seventh ; it measures 2-| inches in length, and shows a depression 

 and perfect convexity of the articular ball, which distinguish it 

 from existing species. The animal was probably about 16 ft. long. 



11. " On Macriirosaurus semnus, Seeley, a Long-tailed Animal 

 with Procoelous Vertebrae, from the Cambridge Upper Greensand, 

 preserved in the Woodwardian Museum of the University of Cam- 

 bridge." By Harry Govier Seeley, Esq., F.L.S., E.G.S., etc. 



The author described a series of about 40 associated and nearly 

 successive caudal vertebrae obtained from one of the deeper phospha- 

 tite workings on Coldham Common. The tail, when complete, prob- 

 ably included 50 vertebrge, and measured 15 feet in length. The 

 articulations of the earlier vertebrae are procoelous, then they become 

 nearly flat, then biconcave, and towards the end of the tail irregular. 

 There are no chevron bones. The neural arch in the earlier part of 

 the tail was supported on pedicles rising from the centrum, de- 

 pressed and devoid of neural spine. The neural arches were of great 

 antero-posterior extent and compressed. The author remarked that 

 although the tail as a whole is more in accordance with the Lacer- 

 tian type than with any other order of true reptiles, the combination 

 of the procoelous character with the absence of chevron bones is 

 unknown to him elsewhere. He added that the metapodium de- 

 scribed and figured by him in 1871, under the name of AcantJiopholis 

 •platypus, may perhaps belong to the foot of Macriirosaurus, in which 

 case the latter would probably indicate a modification of the Croco- 

 dilian type, and the individual to which the tail belonged would 

 have been about 30 feet long. 



12. "On the Mechanism of Production of Volcanic Dykes and on 

 those of Monte Somma." By R. Mallet, Esq., F.E.S., E.G.S. 



The author stated that in 1864 he made a careful trigonometrical 

 survey of the escarpment of Monte Somma, especially with reference 

 to the numerous dykes by which the rocks composing it are inter- 

 sected. He described in detail the phenomena of direction of the 

 dykes, especially as regards the axis of the cone of Vesuvius ; to this 

 direction he gives the name of orientation. Of twenty-seven dykes 

 ten presented an approximately vertical line, whilst all the rest had 

 a sensible dip or " hade." The dykes are in no cases intersected by 

 coherent beds of lava, but in one instance the top of a dyke was 

 stopped by such a bed. Many of the dykes bifurcated or branched, 

 and frequently two dykes intersected each other at considerable 

 angles. These and other circumstances prove that the dykes were 



