34 DEVONIAN FAUNA. 



belong to the same species as the remarkable natural sections last enumerated. 

 Signs o£ the ornament are only seen in a single specimen from Baggy, but they 

 appear sufficient to show its distinctness from the South Devon 0. laterale, 

 Phillips. 



The internal arrangements seem peculiarly perplexing ; while they approximate 

 those oi Actinoceras,t\iey appear to present several characteristics strongly indicative 

 of the Lower Silurian genus Iluronia as differing from Actlnoceras itself, e.g. (1) 

 in the vasiform shape of the rosettes ; (2) in having the tubuli not in the centre 

 but at the summit of the rosettes ; (3) in the rosettes not being interseptal, but 

 sunk into the bases of the septa ; (4) in the sides of the siphunclo being probably 

 unsymmetrical, one side appearing as though it were more evenly nummuloid than 

 the other ; (5) in the siphuncle possibly not occupying a symmetrical position in 

 the shell. On the other hand, in the present species the septa and shell are 

 generally preserved, having only perished in one specimen, whereas in Huronia 

 they are hardly ever preserved. 



Mr. Crick has most kindly taken much trouble in comparing these sections 

 with Cephalopods in the British Museum, and we together came to the conclu- 

 sion that they were so exceedingly like Ormoceras vertebratum, Hall,^ = Ormoceras 

 Bayfieldi, Stokes,^ as in all probability to be congeneric. Hence the question arises, 

 as 0. vertebratum is the type of the genus Ormoceras, whether that genus ought to be 

 united to Actlnoceras after Foord or to Huronia. Mr. Crick regards Stokes's 

 type (which is in the British Museum) as very enigmatical, but its structure 

 seems to correspond with, and to be explained by, our specimens ; and it would 

 seem, if we read the present species correctly, that Ormoceras is only Huronia in 

 a different state of preservation, and that therefore Huronia has as much right as 

 Ormoceras to be classed as a synonym, or perhaps a group, of Actlnoceras. 



The fact that in Huronia the siphuncle is almost always the only part 

 preserved, which is said to prove the extreme tenuity of the shell, does not seem 

 a bar against this, for it is easy to imagine that some species of the genus might 

 have had thinner shells than others, or that shells in a siliceous deposit might 

 have more easily perished than a limestone. Moreover in one of our own 

 sections the siphuncle is the only part preserved, and in the other three the shells 

 are retained in a very imperfect and indistinct condition. It may be noted that 

 Stokes has, on the same plate as his Ormoceras, figured two sections of Huronia, 

 which seem extremely like our fossils. 



At the same time there can be no doubt that the general affinities of this 

 species to Actlnoceras are very great, and if the relationships to Huronia above 

 noted be verified by future specimens they will probably be found to be evidence 



1 1852, Hall, ' Pal. N. T.,' vol. ii, p. 94<, pi. xix, figs. 1 a—j. 



« 1840, Stokes, ' Geol. Trans.,' ser. 2, vol. v, pt. 3, p. 709, pi. Ix, fig. 1. 



