﻿BRITISH FOSSIL CEPHALOPODA. 105 



that it is not a deposit formed after the smaller end of the shell is broken off. The 

 number of small fragments which occur, consisting of one or more chambers with the 

 characteristic ends, shows that the breaking off was not an uncommon circumstance, 

 and very possibly took place during life. On the surface of these caps the deeper 

 furrows lie on the side nearest to the siphuncle ; they are generally median, but 

 occasionally paired ; on the other side are three or more lighter furrows, which 

 occasionally bifurcate. It is difficult to conjecture the cause of these phenomena, 

 which must have had their origin between the formation of one septum and the next. 

 I can only suggest a shrinkage of the mantle during the interval, by which it was 

 thrown into folds, which were perpetuated by an abnormal deposit on their surface. 

 The type is the only large example seen ; the rest are for the most part fragments, 

 showing the ends. 



Relations. — A fragment, figured by Barrande under the title 0. sarcinatum, 

 shows very similar features on a pseudoseptal surface. Though the fossil is of 

 larger size, the section is more elliptical, the siphuncle more nearly central, and there 

 is no great depression round it ; the furrows are all paired, there being no median 

 one ; the surface of the shell is not described as showing any grooves. Though, 

 therefore, the existence of a similar structure binds these two together, there is no 

 proof that they are identical. The grooved surface is not to be matched in any 

 British Orthoceras with which I am acquainted. The surface of 0. fasciolatum, 

 Barrande, is grooved, but the grooves are much closer in proportion, and the whole 

 shell is smaller and more slowly tapering. 



Distribution. — This species has only been found in the one locality near Raeberry 

 Castle, on the east side of Kirkcudbright Bay, where it appears to be tolerably 

 abundant. I have seen 14 examples. 



Orthoceras Maclareni, Salter, PI. VI. figs. 7, 8, 9, 10. 



Orthoceratite, Maclaren, ' Geol. of Fife and the Lowtlnans,' p. 203. 

 1854. Orthoceras Maclareni, Salter in Murchison's ' Siluria,' Foss. gr. 25. 

 1861. „ „ Salter, ' Mem. Geol. Surv. Scotland,' Sheet 32, p. 143. 



1865. „ „ Haswell, ' Silurian Eocks of the Pentlands,' pi. 1, fig. 2, 



p. 23. 

 1873. „ „ Salter, ' Camb. and Silurian Fossils,' p. 186. 



Type. — I have not seen any example which corresponds to the figure given in 

 ' Siluria.' It appears to be compressed ; the rate of increase is 1 in 6. No signs of 

 any aperture are seen. The ornaments are "strong, sharp ridges, imbricating 

 upwards ;" these are irregularly spaced, but on the average are -^ the long diameter 

 apart. They are oblique on the broader side, about 9° in the figure. The septa are 

 nearly direct, and -§ the diameter apart. The length of the fragment is \\ inches, 

 and the greatest diameter § inch. From the Upper Silurian of the Pentland Hills. 



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