Cretaceous Selachians 
87 
Description : — Tooth-plates rhombic in outline, with short crowns con- 
taining enameloid material and with large, bifurcated roots that comprise 
approximately 2/3 of the total height. The crown has no rugose striation 
on its occlusal surface (such as occurs in Myledaphus ), and its outer edge is 
crimped or milled, no doubt to facilitate interlocking between adjacent 
units in the tooth-pavement. Tooth-plates are of medium size, averaging 
less than 1 cm in diameter. 
Discussion : — Because of their worn state the teeth from the Peedee For- 
mation cannot be definitely assigned to the species Rhombodus binkhorsti. 
Despite its superficial similarity to Myledaphus bipartitus Cope, Rhombodus 
appears to be more closely related to the myliobatid Hypolophus than to 
the dasyatids, the skate family. 
The isolated crushing teeth of Rhombodus are quite common in the Late 
Maestrichtian and are found in all marine deposits of that age, especially 
in Morocco, and in Texas, where they are second in number to the teeth 
of Cretolamna s errata. 
FAUNAL COMPARISONS 
The Late Maestrichtian stage of the Upper Cretaceous system is a most 
interesting period, and its vertebrate fauna is not very well known. Some 
of the shark species persisted into the Paleocene while others became ex- 
tinct. 
Table 1, based on data from nine states, shows the stratigraphic dis- 
tribution of the shark species known from the Peedee Formation of North 
Carolina. This chart, of course, is not complete, but will require modifica- 
tion as further discoveries are made. On the basis of current information 
the shark species of the Peedee are characteristic of Late Maestrichtian 
time although some are seen to occur as early as the Cenomanian. 
Considering the Late Maestrichtian shark fauna as a whole, the follow- 
ing forms are known to be of earlier origin: Heterodontus, Lonchidion, 
Pseudocorax, Paranomotodon, Squalus, Ginglymo stoma, Brachaelurus , Mesiteia, 
Rhinobatos, Sclerorhynchus, Ischyrhiza avomcola, Ischyrhiza mira, Ptychotrygon, 
Cretorectolobus , and Protoplatyrhina. Appearing for the first time in the Late 
Maestrichtian are Notorhynchus, Paleogaleus, Scyliorhinus, Dasyatis, Raja , and 
Rhombodus , along with Cretolamna biauriculata and C. serrata. The only forms 
that survived into the Paleocene are Odontaspis, Cretolamna appendiculata, 
Rhombodus, Squalus, Ginglymo stoma, and Rhinobatos. 
ACKNOWLEDGMENTS. — I would like to thank Mr. & Mrs. John C. 
Golden, Jr., of North Charleston, South Carolina for their assistance, es- 
pecially their generosity in donating several of the specimens in this 
study. Thanks go out to Mr. E. Dewey Ross of Mesic, North Carolina, for 
