MOLLUSCA — CEPHALOPODA. 



175 



In the Lower Lias of Dorset are still found very large Gallery 

 phragmocones, but other specimens show the Belemnite type -^g^/e^gg 

 fully developed, with pro-ostracum, ink-bag, and hooked arms. g. 

 Of BdemMites clongatus there is the fine specimen described 

 by Huxley in the Monographs of the Geological Survey and 

 Sowerby's original specimen from Crick tunnel near Daventry. 

 The Middle Lias of Charmouth has yielded the slender 

 Xiplioteuthis elongata, also described by Huxley. From the 

 Upper Lias of Alderton, Gloucestershire, comes a well- 

 preserved pro-ostracum. A monster phragmocone of the 

 Bajocian species Bdemnites gigantcus comes from Germany. 

 The Oxfordian of Trowl^ridge and Christian Malford 

 in Wiltshire furnishes a large series of B. Oiuemi var. 

 Puzosianiis. 



Among Cretaceous belemites, Duvalia dilatata is remark- Table-case 

 able for its guard, swollen in one direction and flattened in 

 the other. Actinocamax is the usual form from Cenomanian 

 to Senonian, being joined by the similar Belemnitella in the 

 latter Age. 



The belemnites did not die out at the close of the Table-case 

 Cretaceous Epoch, but they changed in character. Styrcwo- 

 teuthis orientalis from the Eocene of Syria is still of the older 

 type, but in most the guard was reduced in length, thickness, 

 and calcification. Vasseuria from French Eocene rocks has 

 such a slender yet relatively short guard. In Bdojdcrci and 

 Belopterina the guard is short and somewhat swollen at its 

 end, which makes a slight angle with the phragmocone ; in 

 the former it expands at the sides into two wings. The 

 latter genus is not far removed from the Miocene Spiridirostra, 

 already described (Fig. 85 h). In a later genus Sjnridirostrina 

 (not exhibited) tlie guard is more reduced, and in the modern 

 Spirula it has disappeared (Fig. 85 c). 



Another line of evolution leads, as previously explained. Wall-case 

 from Bdojdera to Bdoscpia (Fig. 85 d) of which many "^^ 

 specimens from the London Clay and Bracklesham Beds, 

 are shown. Sepia itself is exhibited from later Tertiary 

 rocks (Fig. 85 e). 



Of those sheathed forms in which the calcification of the Wall-case 

 shell underw^ent a gradual reduction, the earliest know^n is 

 FhragmotctttJds from the Upper Trias. The next in age is 

 Geoteuthis, of which large specimens from the Lower Lias of 

 Dorset are exhibited. These and the smaller specimens from 

 the Upper Lias of Wiirtemberg and Normandy show an 

 expanded pro-ostracum, divided lengthwise into three areas, 



