vi APPENDIX A. 
squarer species, and in some which are probably compressed 
laterally ; for I find that the line where the usual transverse 
ribs are bent or broken at about the middle of each lobe, is not 
really in the middle in all cases, but is nearer the dorsal and 
ventral angles than the lateral ones; and again, the two lobes 
which form the dorsal side are sometimes wider than those two 
which form the ventral face. Of course this will only apply to 
the symmetrical species, and not to those which have been 
described and figured as rhomboidal, with the opposite sides 
only equal. And there are several other forms of this remark- 
able genus. 
C. SowrrsByi1, Defrance. 
Syn.—C. quadrisulcata, Sowerby, Sil. Syst. t. 12. fig. 22. C. 
Sowerbyi, Defrance, Dict. Sc. Nat. and De Blainv. Mala- 
cologie, 377, Pl. 14. fig. 2. De Vern. and Keyserl. Geol. Russ. 
t 24. f. 5. 
Variety 2 C. gerolsteinensis, De Vern. and d’Arch. Geol. Trans. 
2nd Series, Vol. 1V. | 1.81. fig. 5. 
Sp. Ch.—Rather quickly tapering, depressed dorsally, sur- 
face of the lobes gently and regularly convex, with sharp 
transverse ribs continuous and angularly bent (not arched) 
over the submedian line, and ending on a higher level at the 
dorsal than at the lateral furrows; longitudinal strie regular 
between the ribs, which they render granular in parts. [Septum 
finely striated in the longer diameter, and with a central com- 
pressed umbo ]. 
After examination of numerous specimens, I can find but 
little characteristic differences in the variable strie between 
this and C. 4 sudcata. In the latter the transverse ribs are fine 
or coarse, and either angularly bent or arched continuously 
over the submedian line, or broken at this point and inserted 
one above the other ; but the general form is more elongate than 
in C. Sowerbyi,—the section too, is square; in our species it is 
an acute rhomb, and this is not the result of pressure, for it is 
observable in every specimen. The shell figured in the Silu- 
rian System is terminated abruptly at the smaller end by a 
septum, which has been particularly described by Mr Sowerby, 
and is a very curious thing. De Koninck says that sections 
haye been repeatedly made, and no septa found in true 
Conularia. Yet this is certainly a continuation of the general 
surface, and has a central umbo, which might have been pierced 
by a siphon. I beg to offer as an explanation of it, that the 
apex of the shell had been broken off, and the septum was the 
animal’s attempt to fill up the hole as in Cuvieria ; this may 
account for the ornamented surface, and perhaps for the acu- 
minate central point. But Hall speaks positively of septum and 
an excentric siphuncle in this species, so that the matter is 
still open to observation, Conulariu teres Sow., which has real 
septa, is by common consent allowed to be a Cephalopod. 
Loc.—Upper Silurian, Westmoreland ; Cambrian, Bala, N. 
Wales. The variety with fine strie, which we have referred 
to C. gerolsteinensis, De V., occurs in the Upper Ludlow, Kendal. 
Ref. Pl. 1.L. fig. 24. 
Syv.—C, Gervillei, De Vern. and d’ Arch, Geol. Tr. 1. e.t. 29, 
Sig. 8 (not fig. 4)? 
Sp. Ch.—Moderately conical, compressed a little laterally, 
ventral lobes smaller than the dorsal; lobes flat, crossed by 
C. sustiuis, Sp. Nov. 
very fine close ribs, continuously arched over the submedian 
line, which is nearer the dorsal and ventral than the lateral 
furrows ; longitudinal strie very faint. 
The extreme fineness of the ribs distinguish this species 
from all yet described, except, perhaps, Eichwald’s C. Buchii, 
and De Verneuil’s C. Gervillei, from the Rhenish strata. Un- 
fortunately, of the latter we have’ not ‘specimens of similar age 
for comparison, and that species is not described as inequilateral, 
nor does it taper nearly so much as ours. Nor can we identify 
Eichwald’s imperfectly described C. Buchii, Sil. Syst. of Estho- 
nia, p. 111, since that species is said to be more rapidly conical 
than C. quadrisulcata in the young part,—ours is less conical. 
The chief peculiarity of our shell is the inequality of the 
lobes, and the lateral, not dorsal, compression of the form. 
Agreeably with this, the submedian line is considerably nearer 
those furrows which mark back and front; attention to this 
character will probably enable us in all cases to ascertain which 
portion of the body we observe. 
Loc.—Collinfield; Brigsteer; and Benson Knot, Kendal, 
in Ludlow Rocks. 
Orrnoceras Vacans, Salter. Ref. Pl. 1. L. fig. 28 and 29. 
Syn.— O. vagans, id. Geol. Quart. Journ. Vol. V. Pl. 6. fig. 6. 
Sp. Ch.—Smooth, long-tapering when young, more conical 
when old; septa broad elliptical, oblique on the longer axis, 
moderately distant in the young shell, distant more than the 
diameter in middle age, and by less than one-fourth of it when 
old; deep, cup-shaped ; siphuncle prominent, central. 
Var. «.—Septa in middle and old age much closer. 
Var. 8.—Conical in the young state. 
This common species differs from O. distans, Sil. Syst., in the 
less size and in the position of the siphon. A large series of 
specimens shews how much care is necessary in establishing 
species on the distance of septa and general conic form, unless 
the species distinguished are known in similar ages. In its 
youngest state, when the growth was comparatively feeble, 
the septa, which may be considered as varices of growth, are 
not far apart; in middle-age vigour, if it be not checked by 
untoward causes, the growth is quicker, and in full age it is 
proportionally slower, while the diameter expands as the shell 
attains its full size, and when probably the ova are developed. 
This sudden increase of diameter is sometimes very marked in 
Orthoceras and the allied genera, and we think may be attri- 
buted to the cause above mentioned, viz. the enlargement of 
the reproductive organs. 
Loc.—Bala limestone, N. Wales ; Coniston, Westmoreland ; 
Cambrian. 
O. Bacuuirorme, Sp. Nov. Ref. fig. 27. Pl. 1. L. 
Syn.—O. linearis, Munst. Beitr. Heft. 3. t. 19. fig. 1? 
Sp. Ch.—Long, linear, smooth, with a deep sinus in the 
lines of growth on one of the flatter sides; section long-oval ; 
septa flattish, a little oblique, about one-fourth their diameter 
apart ; siphuncle central. 
The portion figured hardly tapers at all, but we cannot 
estimate the length from this circumstance ; and as it is an inte- 
rior cast, there may be fine transverse strie on the outside ; if so, 
it would be very difficult to separate it from O. linearis, the 
