396 A. H. Foord — Ammonites in the British Museum. 



extremely attenuated and trencliant form of the adult shell. In this 

 species the whorls are deeply embracing, so that very little is seen of 

 the inner volutions. (Table-case 68, Wall-case 12.) 



The -^GOCERATiD^ are restricted to one genus, jEgoceras, of the 

 Lias, ^goceras capricornus, Fig. 12 [A. capricornus zone of the 



Fig. 11. 



Arietites obtusus, Sow. (Lower Lias.) 



Lower Lias), ^. Davcei (Fig. 13), and ^. armatum of the Lower 

 Lias are some of the most characteristic species. The last-named 

 species is conspicuous for the long spiny processes projecting from 

 the sides of the shell. (Wall-case 12.) 



The family Poltmorphid^ has been constituted to contain certain 

 genera which have been separated from the iEaooERATiD^ on the 



Fig. 12. 



Fig. 13. 



^goceras capricornus, Schloth. 

 (Lower Lias.) 



^goceras Davcei, Sow. 

 (Lower Lias.) 



one hand and from the Harpooeratid^ on the other. It is notable 

 for the variations undergone by the shell in passing from the young 

 to the adult stage of growth. Liparoceras BecJiei (Middle Lias) is 

 a well-known species with a highly ornate shell. Bammatoceras 

 Sowerbyi (Lower Oolite) has a keeled margin in the young shell 



