440 DR. J. E. GRAY ON A NEW SPERM WHALE. [May 23, 
CaTopon (MEGANEURON) KREFFTII, Sp. nov. 
The atlas vertebra oblong transverse, about one-third wider than 
high ; the lateral processes only a little produced beyond the articular 
surface, with an arched edge; the lower edge arched ; the neural 
arch low, broad, with a slight central prominence on the upper sur- 
face; the canal for the spinal marrow very large, circular, rather 
contracted on the sides above, and then dilated, becoming oblong and 
transverse. 
The atlas is thin, high, being only about one-fourth wider than 
it is high. The lower and lateral margins are arched, the lower 
edge being the most so. The neural arch is low, transverse, with a 
nearly straight lower edge. It is thickest in the middle. The 
upper surface is shelving on the sides, with an angular central pro- 
minence. 
The central aperture is very large, nearly circular, and dilated 
above into an oblong transverse aperture, which is rather wider than 
the widest part of the central circle. The front articulating surface is 
horseshoe-shaped, continued to the upper outer angle, and obliquely 
shelving off on the upper edge to the base of the oblong part of the 
aperture. The articulating surface of the hinder side is similar; 
but the articulating surface is shorter at the sides, and transversely 
truncated in a line with the middle of the upper, oblong, transverse 
opening (figs. 1, 2). 
Fig. 2. 
Fig. 1. Front of atlas of Catodon krefftit. 
2. Hinder side of ditto (reduced). 
The second and other cervical vertebree are all united together into 
one mass, anchylosed by their bodies, lateral processes, and neural 
arches. The neural arches form a triangular mass, which is strongly 
keeled on the central line; and the keel is stronger and produced 
into an acute point at the hinder end (figs. 3, 4). 
The lateral processes of the second, third, and fourth vertebre are 
produced and united into a broad, thick, angular process, which is 
ae ». 
