ORTHOCERAS. 29 



Description. — Shell very large, decreasing slowly at tlie rate o£ 1 : 12. Section 

 oval, in ratio, 8 : 7. Chambers narrow, being in height about one seventh or 

 one eighth the width of the shell. Septa sloping very obliquely across the 

 short diameter. Siphuncle sub-circular, about one half an inch in diameter, sub- 

 central, consisting of long vasiform or ellipsoidal beads, suddenly constricted into 

 narrow concave necks at the septa, their greatest and least widths being as 7:5. 

 Test about 3 mm. thick (in largest specimen), showing no markings. 



Size. — A large specimen is five inches by three and a half inches in transverse 

 diameters, but is probably slightly compressed. 



Locality. — A large specimen from Top Orchard Quarry is in the Barnstaple 

 Athengeum, and another, slightly smaller, from " North Devon " in the British 

 Museum. The original of Phillips's figured specimen (fig. 206 h) from the Pilton 

 Beds is in the Museum of Practical Geology. 



BemarJcs. — These specimens are fragmentary and insufficient to identify the 

 species, which evidently was very large, probably several feet in length. Whether 

 the other specimen figured by Phillips (fig. 206 a) is identical I am not quite sure, 

 as, according to its figure, its tapering is more rapid, viz. 1 in 5 or 6 instead of 

 1 in 12 ; but it is possible that this apparent difi'erence may be due to accidental 

 circumstances. 



Neither is it at present clear that these Devonian fossils have any right to the 

 name of Sowerby's Silurian 0. Ludense. 



Until more is known about its specific characters, it appears safer not to 

 attempt to identity it with species belonging to a different formation. 



It appears from the character of its siphuncle properly to belong to the genus 

 Orthoceras, and is therefore probably distinct from the Lummaton species 

 described by me as Actinoceras devonicans,^ and from A. striatum, with which. 

 M'Coy ^ and Foord ^ had doubtfully identified it. 



Affinities. — Orthoceras Pelops, Hall,* appears to equal it in size, and to be 

 similar in many characters, but we have not sufficient data for full comparison. 



2. Oethoceras speciosum, Milnster. Plate IV, fig. 4, 4 a. 



1888. Oethoceeas, sp., Foord. Catal. Foss. Cephal., pt. 1, p. 98. 

 1890. — SPECIOSUM Whidborne. Dev. Faun., vol. i, p. 149, pi. xv, 



figs. 7 ?, 8—10. 



1 Vol. i, p. 120, pi. xii, figs. 8, 8 a. 



2 1852. M'Coy, ' Brit. Pal. Toss.,' p. 405. 



3 1888, Foord, ' Catal. Foss. Ceph.,' vol. i, p. 187. 



* 1879, Hall, 'Pal. N. T.,' vol. v, pt. 2, p. 233, pi. xxxv, figs. 1—3; pi. xxxva, figs. 1—6; 

 pi. xxxvii, figs. 3, 4 ; pi. IxxviiiB, fig. 2. 



