64 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 62. 
cross section shows a solidified core or tooth pulp perforated by a 
minute channel for the nerve. In thissection the cementum and the 
dentine are approximately equal in thickness while the diameter of 
the pulp cavity is fully twice the width of either of the above layers. 
The roots are joined at the base by a short thin isthmus which is 
continued upward as a well-defined groove and terminating below the 
crown. The posterior root is stouter than the anterior. The enamel 
crown of the molar is ornamented with longitudinal striae; these 
striae are more pronounced on the external margin than on the 
internal. The apex of the crown is missing and the posterior cutting 
edge is incomplete. The worn surfaces of the enamel indicate that 
three cusps were originally present on the posterior edge though they 
were worn down to their bases. The anterior cutting edge is missing. 
The fragment of the jaw (pl. 17, fig. 1¢) which held this molar is so 
worn that little information can be obtained regarding its former 
appearance. It possesses two alveolae for two-rooted molars. The 
curvature of the outer surface of this fragment suggests that it may 
be a portion of the left maxilla. 
MEASUREMENTS FOR MOLAR AND FRAGMENT OF JAW. 
Greatest length of crown. EEO TE REORDER IM em a are ENON pa ears "29 
Gres tread niet tga an Dee eee Oran pee ene 
Greatest diameter across combined roots pole crown. he REL EL BM SGRS 
Gréatestthickness‘of posterior root ..32. 9.2849 920082 2 Ate oe oe IE EE. 2 
Greatest width of posterior root..........- 18.5 
Length of posterior root measured in a price tee) from center oh base’ of 
crown to tipssf7e52 54 60. 5 
Length of Witerior mer ied t ina A bemighe ine foal center ef nage of crown 
to tip.. 2 PEL DID 8 
Distance from base a lonataclie crown ve onier ede ¥ almeniact pune h. | seh 
Greatest lencth of fragment of jaw...-...-.---.-2 4: -. 2. adhe eee eee Oe 
Greatest depth of fragment of jaw.. - 39 
A nearly perfect crown abe a ae roulan al 17, ES, ae 2) was 
obtained by William Palmer on one of his trips to Chesapeake Beach. 
Reference is made to a number of broken molar teeth in Mr. Palmer’s 
notes, but the teeth are not described in such a way that one can 
identify them. According to these notes all the teeth were obtained 
from beach débris and hence there is no means of associating the 
specimens with any particular zone. 
Specimen, No. 10726, Division of Vertebrate Palaeontology, United 
States National Museum. 
Occurrence.—Chesapeake Beach, Calvert County, Maryland. 
The molar crown is high and the enamel is rugose, the striae being 
coarser at the base than at the apex. There are three accessory 
cusps on the posterior edge. The anterior edge is missing but there 
are no peculiarities which would suggest the existence of accessory 
