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A NEW FOSSIL PORPOISE FROM MARYLAND. 



series. 



The total number of teeth originally present, as indicated above, was about 

 106, of which 43, or about two-fifths, are preserved. As those available are of 

 different forms and sizes, and are apparently from both jaws, it is allowable to 

 suppose that they represent quite fully the different forms characteristic of the 



These teeth have been arranged and numbered in accordance with certain 

 indications which will be described below, beginning at the posterior end of the 

 series in each jaw. 



The series as a whole has the following characteristics: The largest teeth 

 have a length of 29 mm., and a maximum diameter of 5 mm. The smallest 

 teeth are 20 mm. long, and have a maximum diameter of 4 mm. The crown 

 of each tooth occupies about one-third the length of the tooth (except as indicated 

 below) , and is acute and strongly curved inward, especially at the posterior end of 

 the series. The posterior maxillary tooth on the left side has two distinct cusps, 

 one in front of the other, and a less prominent cusp behind them. On the 

 right side, the cusps are less prominent. Three or four teeth at the posterior 

 end of the series, on either side, present an antero-internal and a postero-internal 

 basal cusp, and below each a smaller one, which should perhaps be regarded as 

 merely a prominence on the cingulum. Indications of these basal cusps are 

 distinguishable on some of the more anterior teeth, but die away and disappear 

 at the distal end of the series. The apex of the crown is most strongly incurved 

 at the posterior end of the series and less so anteriorly. As already mentioned, 

 each tooth has an anterior and a posterior longitudinal ridge on the crown. At 

 the posterior end of the series, the anterior ridge is divided into two, which 

 diverge toward the base of the crown. The amount of divergence is large in the 

 teeth at the posterior end of the row, but diminishes gradually on each succeeding 

 tooth anteriorly, and at the distal end of the row is reduced to zero, the anterior 

 teeth presenting only a simple ridge anteriorly and a similar one posteriorly. 



The cingulum is not very distinct on any of the maxillary teeth, except at 

 a point just internal to the base of the posterior longitudinal ridges, where in 

 some cases, especially near the middle of the series, it forms an appressed, raised 

 area, with a crenulate upper margin. In other instances, it is represented only 

 by a horizontal basal extension of the ridge. 



The rugosities of the enamel of the crown are sufficiently coarse to be dis- 

 cernible with the naked eye. They consist of very numerous rounded ridges 

 of varying size and length, and are for the most part longitudinal. In the 

 anterior teeth, as already mentioned, the rugosities, though present, are much 

 less distinct. 



The roots are slender, elongated and curved backward at the extremity. 

 They are somewhat gibbous near the junction with the crown. Both the upper 

 part of the root and the crown are flattened anteriorly and posteriorly 



The mandibular teeth are similar to the maxillary teeth in form, but 



the 



posterior tooth the accessory cusps are less distinct than in the penultimate 

 tooth, and the two or three which precede it. In these there is a distinct postero- 



■n 



