﻿BRITISH FOSSIL CEPHALOPODA. 163 



chamber, seen in some, is crowded with smaller Orthocerata, with their apices in the 

 same direction as that of the larger shell. These are so close together that the 

 improbability of their being accidentally enclosed is increased a hundredfold, and 

 three examples showing the same features force on us the conclusion that the small 

 ones are related to the large. The walls of the body-chamber seem almost to have 

 been soft, and more or less forced out of shape by the small shells within. The septa 

 in Portlock's example are direct, but somewhat undulating ; they are distant ^ the 

 long diameter, and are seen to be produced below into long necks ensheathing the 

 siphuncle, as is characteristic of Endoceras. Their general convexity is -§ the long 

 diameter. The siphuncle has a diameter ^ of the minor axis of the shell, and its 

 centre is situated about f across the latter line. The little shells are nearly circular 

 in section, taper at the rate of 1 in 10, have direct septa about ^ the diameter apart, 

 and a large but nearly central siphuncle. These characters would agree best with 

 0. politum, but the large size of the siphuncle shows they may really be the young 

 of the specimens containing them. The greatest length of the large ones is 4 inches, 

 and the greatest diameter is 3 inches. 



Relations. — I can only find one difference between our English and the American 

 form, and that is the lateral siphuncle of the latter ; in the absence of proof, however, 

 that it is really so lateral as in E. vertebrate or E. duplex, it will be well to leave the 

 name, adopted by so many previous authors, untouched. 



Distribution. — In the Bala Beds of Desertcreat (1) and of Bala ? (.1) ; x and 

 in Lower Silurian rocks of Waterford (3). 



It is also recorded by Nicholson from the Green Slates of Ingleton, and by 

 Harkness also from the Dufton Shales of Westmoreland. 



Orthoceras (Endoceras) festustans, Blake, PI. XVII. figs. 3, 3a. 



Type. — The section is not quite regular, and the specimen may have been 

 therefore somewhat compressed ; at present it is elliptic, having the radii in the 

 ratio of 4 to 5. The rate of increase of the long diameter is 2 in 15. No 

 body-chamber or ornaments are seen. The septa are slightly undulating, and are 

 distant -^ the diameter. They form long necks in the neighbourhood of the 

 siphuncle, which they are seen to cross on the worn surface at a distance of one 

 chamber towards the apex. Their convexity is about ^ the diameter. The 

 siphuncle is cylindrical, having a diameter of J the longer diameter of the shell ; it 

 lies close against the side on the shorter diameter. The length seen is 3-g- inches, 

 and the greatest diameter 3-^- inches. 



1 The specimen figured by Salter, ' Mem. Geol. Surv.,' vol. iii., pi. 24, fig. 6, but not named, may- 

 belong here, as it agrees so far as its characters are shown, except in its perhaps abnormal curvature. 

 There is also some appearance in it of a large siphuncle, but this is doubtful. It agrees with no other 

 British form. 



Y 2 



