A. H. Foord — On the Genus Filoceras. 541 



III. — On the Genus Filoceras, Saltee, as Elucidated by 

 Examples lately discovered in North America and in 

 Scotland.^ 



£y Arthur H. Foord, F.G.S. 



rpHE genus Filoceras was founded by J. W. Salter in 1859 ^ upon 

 I the siphnncle of a shell closely allied to Endoceras. It was 

 supposed by Salter that the invaginated sheaths observed in the 

 siphnncle of Filoceras " represented the siphuncle and septa 

 combined," the septate part of the shell not being preserved in the 

 specimens described by him. 



A year after the appearance of Salter's memoir, E. Billings (at that 

 time Paleeontologist to the Canadian Geological Survey) described a 

 fossil from the Calciferous Sandstone (= Tremadoc) under the name 

 of Filoceras Canadense.^ This exhibited the septate part of the 

 shell in conjunction with the siphuncle. 



The general form of this species was well characterized by Billings 

 as that of a " short, thick, curved Orthoceratite." 



This appears to have been the first discovery of the septa of 

 Filoceras, associated with its siphuncle, for the generic identity of 

 Salter's and Billings's species is now put beyond all doubt. 



Again, in 1881 Sir William Dawson * described a new species of 

 Filoceras (P. amplum) from the Calciferous Sandstone of Lachute, 

 near Montreal, which threw much new light upon the internal 

 structure of the shell. 



But the most complete examples of Filoceras hitherto met with 

 were collected in 1885 by Messrs. Seeley and Brainerd, at Fort 

 Cassin, in the State of Vermont, from rocks considered to be of the 

 age of the Birdseye Limestone (= the Lower Llandeilo, nearly). 

 These fossils were described and beautifully illustrated by Professor 

 E. P. Whitfield, of New York,^ who was enabled to show by means 

 of almost perfect specimens, the body-chamber, septa, siphuncle 

 (in place), and even the test of the species, which he very appro- 

 priately named Filoceras explanator. 



M. Barrande,^ whose information about Filoceras was very scanty, 

 constituted it a subgenus of Cyrtoceras, on account of its curvature, 

 and Professor Blake ' disposes of it in the same way, though only 

 provisionally, for he remarks, '■' The organism, whatever it is, must 

 wait further elucidation by materials not yet extracted from the 

 rocks." 



Finally, about four years ago, Mr. B. N. Peach, of the Geological 

 Survey of Scotland, found specimens of Filoceras at the typical 

 locality, Durness, Sutherlandshire, in which both septa and siphuncle 



1 The substance of this paper was read before the British Association at Manchester, 

 in September last. 



^ Quart. Journ. Geol. Soc. vol. xv. p. 376. 



' Canadian Naturalist and Geologist, vol. v. p. 171. 



* Canadian Naturalist, new ser. vol. x. No. 1. 



5 Bull. Amer. Mus. Nat. Hist. vol. i. No. 8, p. 323, pi. xxviii. New York, 1886. 



6 Syst. Sil. de la Boheme, vol. ii. Texte, v. 1877, p. 905. 

 ■^ British Foss. Cephalopoda, pt. i. p. 186. 



