anv. 16, TWO SQUALODONTS FROM MARYLAND—KELLOGG. 59 
ess and the tenth exhibits the line of fusion of the diapophysis with 
the parapophysis. 
The facets for the post zygapophyses of the preceding vertebra 
are large and well developed, sloping obliquely internally and ven- 
trally. The prezygapophyses have been broken off but were, appar- 
ently, large processes. The neural canal is much smaller than that 
of the anterior dorsal. An increase in the depth as well as length of 
the centrum should be noted. 
The three lumbars found with the skull are imperfectly preserved. 
The first and second lumbar vertebrae (pl. 11, figs. 1-2; pl. 12, figs. 
1-2; pl. 13, figs. 1-2) possess complete neural arches and the lower 
portion of the neural spine. The neural arch does not occupy the 
full length of the centrum and the posterior margins of the arch 
are strongly concave. The prezygapophyses were large as originally 
preserved but in the vertebrae under discussion only the broken edges 
reveal their former presence. The transverse processes are thin and 
are narrower than the centrum. The distal ends of all are broken 
or damaged in some way. The neural canal is narrow and high. 
The third lumbar is so badly damaged that little can be said concern- 
ing it. 
RIBS. 
The number of pairs of ribs possessed by this squalodont can not 
be determined definitely from the material at hand, which is limited 
to 10 ribs. It appears, however, that there were present originally 
at least 11 pairs of ribs. The whole ribs and fragments were care- 
fully compared with associated skeletons of living cetaceans and the 
following determinations are advanced tentatively. 
A considerable portion of the first rib (pl. 16, fig. 1) belonging to 
the left side is preserved. It is relatively thin, broad, and somewhat 
flattened, and the curvature at the broken end indicates that it was 
slightly expanded distally. The articular facets on the head and the 
tubercle are present but are poorly defined. The neck is relatively 
narrow. The proximal portion is bent at right angles to the shaft 
and the neck is turned inward. The left rib (pl. 16, fig. 2) of the 
second pair of ribs is in a better state of preservation than some of 
the others and the shaft is more nearly of equal width throughout. 
The tubercle is well developed, the neck shortened, and the shaft 
slightly thickened. The distal end is rounded and the surface for the 
sternal cartilage is lightly pitted. The third rib (pl. 16, fig. 3) belong- 
ing to the left side shows a narrowing of the neck and aslight reduc- 
tion in the extent of the tubercle. The curvature of the shaft is 
more even, and the angle is not so noticeable as in the first and 
second ribs. 
The rib which is assumed to represent the fourth on the right side 
(pl. 16, fig. 8) exhibits a noticeable lengthening of the neck and a nar- 
