ART. 16, TWO SQUALODONTS FROM MARYLAND—KELLOGG. 55 
shallow, and consists of a thin shell of bone. Posteriorly the frame 
diminishes in thickness and in the region anterior to the coronoid, 
and on the internal face it is no thicker than blotting paper and very 
fragile. The internal portion of the ramus consists of an expanded 
papyraceous area opened for the whole length of the mandible by an 
enormous inferior dental canal. The proximal portion of the mandi- 
ble is deep and thin, gradually tapering in depth rostrally though 
increasing in width. The external surface is convex and the internal 
somewhat flattened. The coronoid portion of the mandible curves 
inward and the distal portion outward. The alveolae shift with the 
postero-anterior curvature of the mandible from a horizontal to a 
lateral position. 
In general outline the mandible of this Maryland squalodont recalls 
Squalodon zitteli”® from the Miocene of Bavaria. The length of the 
symphysis, the proportions of the ramus, and the large size of the 
anterior alveolae are features common to both specimens. 
TEETH. 
More than 50 years ago two fragments of a squalodont skull, ob- 
tained from the Calvert formation of Charles County, Maryland, were 
submitted to Cope by James T. Thomas. Each of these fragments 
possessed three serrate two-rooted molar teeth. In describing these 
teeth, Cope ®*° compares them with two European species and then con- 
cludes they are referable to Leidy’s form Squalodon atlanticus. The 
measurements given by Cope and the figures accompanying Leidy’s * 
report agree with the size of the alveolae of the skull discussed in the 
present paper. Certain features pointed out by Cope and Leidy, 
such as the ‘‘ more elevate conic apex’’ of the crown and the “less 
strongly wrinkled’”’ enamel, suggest a close relationship with the 
present species. On the whole there is considerable resemblance 
between Cope’s squalodont and Squalodon calvertensis, taking into 
consideration the size and shape of the teeth, the ornamentation of 
the enamel, and the number of accessory cusps. In addition, these 
two specimens were obtained from deposits belonging to the Calvert 
formation. 
The squalodont described by Cope and the present specimen are 
quite different from Squalodon atlanticus. The four teeth shown on 
Leidy’s plate represent the third to the sixth molars, inclusive, judg- 
ing from comparative measurements and size of the accessory cusps. 
These molars are not represented among the teeth preserved with the 
skull under discussion. Eleven isolated teeth were found embedded 
in the matrix surrounding the skull. An examination of the alveolae 
of the skull and mandible shows that the teeth were implanted ob- 
79 Zittel, K. von, Palaeontographica, Stuttgart, vol. 24, pl. 35, figs. 1, 3, 1876-77. 
80Cope, E. D., Proc. Acad. Nat. Sci. Philadelphia [vol. 19], pp. 132, 153-154, 1867. 
81 Leidy, J., Journ. Acad. Nat. Sci. Philadelphia, ser. 2, vol 7, pl. 30, fig. 18, 1869. 
