240 J. F. WHITEAVES ON A NEW SPECIES OP AMMONITE. 



tubercle, whose summit is obtusely rounded, and each branch bears a similar tubercle 

 near the outer edge of each side of the periphery. The secondary folds also each bear a 

 single tubercle on both sides, near the margin of the periphery, but become obsolete and 

 consequently devoid of tubercles on the umbilical margin. In the larger of the two half- 

 grown specimens, the primary folds are simple and do not bifurcate, but bear transversely 

 elongated tubercles on the umbilical margin, and alternate with shorter secondary plica- 

 tions. In both specimens the primary and secondary folds are continuous across the peri- 

 phery, and the siphoual region is entirely devoid of any kind of keel. 



On the largest examples collected, the radiating folds become nearly or c[uite obsolete, 

 and the outer A^olution bears a circle of seven or eight widely distinct, very large and 

 l^romiuent conical tubercles aroviud and on the umbilical margin, and about double that 

 number on each side, near the outer edge of the periphery. In addition to the tubercles, 

 the surface is marked with coarse and irregularly disposed radiating striœ, together with 

 a few indistinct remains of the folds which characterized it at an earlier stage of growth. 

 At all stages of growth the tubercles, whether large or small are placed at a right or 

 nearly right angle to the sides of the shell. 



The generic position of this species must, of course, remain doubtful until the suturai 

 line of the latter shall have been observed. In the meantime, however, judging by analo- 

 gies in external form and Surface ornamentation, the present species seems to be somewhat 

 nearly related to the Buchicerus Swallovi (the Ammonites Swallovi of Shumard) of the Utah 

 Cretaceous, and may, therefore, be provisionally referred to that genus, under the name 

 Buchkeras (?) cori/nf/oii, although it is quite as likely to be an Acanthoceras or an Hoplites. 

 The close involution of its whorls and the ornamentation of their sides are very like those 

 of some species of Placenticeras, but the broad siphonal edge of the Peace River shell seems 

 to forbid its reference to that genus. The most prominent characters of B. cornatum are its 

 small umbilicus and the large size of the tubercles on the adult shell. In B. Sivallovi, the 

 umbilicus is stated to be so large as to exhibit '' a large part of each of the inner volutions " ; 

 the nodes or tubercles on the sides of the shell are comparatively small, and there is a double 

 row of tubercles near the margin of the periphery, whereas in B. cornutum there is only a 

 single row. 



