8 
Genus, pakacephalites nov. 
Genotype, Paracephalites jucundus nov. 
Sphaerocone, flexicostate [passing to platycone, smooth] 1 ; suture-line 
fairly elaborate, [becoming less so in smooth stage]; EL (external lobe) 
longer than LI (first lateral lobe), L2 (second lateral lobe) about three 
parts as long as LI ; umbilicus gradate with convex walls, the chord of the 
arc at right angles to the plane of the conch. 
The primary ribs begin at contact-line of whorl, passing over umbilical 
wall with a curve concave forwards, they bifurcate a little beyond the 
umbilical wall, about on line of S2 (second lateral saddle), and there are 
occasional intercalate ribs — the secondary ribs are about versiradiate in 
direction and pass straight over venter. All ribs are rounded and not of 
very strong relief. 
The genus differs from Macrocephalites in having a much simpler 
suture-line. 
A few words may be said about Ammonites mdcrocephalus Schlotheim. 
This was named by Schlotheim in 1813 (p. 70). The protolog reads as 
follows: a Ammon[ites] macrocephalus Oryct. nor suppl. T.XIL F. 8.” Thus 
the figure in Baier (Suppl. PI. XII, f. 8), is the protograph and the specimen 
which it depicts is the holotype. The protograph has been reproduced by 
Blake (p. 43): it represents a sphaerocone, something like a cricket ball 
with a small umbilicus, fairly strong ribs, and, presumably, a rather elab- 
orate suture-line. This form would not at the present day be regarded 
as the same species nor even as the same genus as the Macrocephalites 
macrocephalus Zittel, which is the genotype of Macrocephalites. Zittel 
happens to have followed approximately d’Orbigny’s incorrect determin- 
ation of Schlotheim’ s species. 
It is obvious that Paracephalites in shape, rib'bing, and, possibly, 
suture-line is nearer to Am. macrocephalus Schlotheim, than it is to Macro- 
cephalites. But it would not, therefore, be advisable to say that Schlo- 
theim’s species is a Paracephalites: observation of certain English material 
which has a more satisfactory similitude to Schlotheim’s species suggests 
that still another genus is involved and that the complexity to be unravel- 
led in regard to Macrocephalitids is far greater than the hitherto very 
casual naming of forms expresses. 
* 
Paracephalites jucundus nov. 
(Plate II, figures 1-3) 
Holotype No. 8600; loc. 6593, Grassy mountain 
Proportions, 2 S. 34,-, 65,-, 46, 47, 65, 23 
Size of specimen, c. 50 mm. Maximum size, e. 80 mm. 
Proportions of suture line of 22 mm. breadth of whorl, EL 64, LI 
57, L2 36 per cent 
Proportions of suture-line at 38 mm. curve of whorl, EL 37, LI 33, 
L2 21 per cent 
1 The words placed in square brackets in this and other generic descriptions refer to characters which are taken 
from specimen or specimens other than the genotype. 
1 For explanation of method of stating proportions and meaning of symbols See S. Buckman, 2, p. viii (1913). 
