The rear end of the center. is lower than the anterior, a modification also present in the lumbar spine of Kentriodon. 10 PROCEEDINGS OF THE NATIONAL MUSEUM VOL.69 Comparison of skulls of Kentriodon pernlx and DelpMnodon dividum Cope—. The end of the rostrum formed by the premaxillae and at least eight of the teeth on each side are contained in this bone.
ART. 19 A MIOCENE PORPOISE FEOM MARYLAND KELLOGG 11 Comparison of skiUls of Kentriodon permx and Delphinodon dividum Cope —
Anterior to the premaxillary foramen, the internal jDortion of the premaxilla is separated from the external border by the first-mentioned groove; this triangular band narrows rapidly and. With the exception of a short interval in front of the respiratory tract, where the inner edges of the premaxilla almost meet, the mesostral groove is open throughout its length. The vomer increases in Avidth from its anterior end to the airway, and rises near the proximal end of the mesorostral groove to the level of the plug-like presphenoid.
ART. 19 A MIOCENE PORPOISE PROM MARYLAND — KELLOGG 13
In front of the orbit, the antero-external angle of each maxilla forms, forming an apophysis. The tears are closely attached to the supraorbital process in the front and are barely visible from a dorsal view. Seen from the dorsal view, the frontals are largely hidden by the over-i^spread cranial plates of the maxillae and the slender premaxillae.
ART. 19 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 15 The walls of the brain case were too thin to withstand crushing and
An extremely thin and almost filamentous styliform process of the jugal extends below the orbit. Fortunately, the entire styliform process of the right jugal bone is preserved on the first skull. The vomer first appears on the ventral surface of the skull about 60 mm.
AKT. 10 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 21
22 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 69
ABT. 19 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 23
24 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. GO
ART. 19 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 25
26 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. G'.)
ART. 19 A MIOCENE PORPOISE FROM MARYLAND — KELLOGG 27
The posterior process is borne on a shorter neck than in Prodelphinus malayanus and the articular facet is considerably larger. The dorsal surface of this leg bone is traversed by a shallow mesial groove that curves from point to point. The internal portion of the coccygeal bone is larger, thicker and more nearly oval in outline than that of Prodelphinus malayanus.
The dorsal edge of the thin outer lip of the tympanic bulla is fused to the ventral surface of the accessory ossicle along the outer edge of this ovoid internal structure. Seen from the ventral side, it appears that the inner edge is biconvex and the outer edge is convex-concave. The head of the left malleus (Fig. 12) has the same shape as in Prodelphinus malayanus (Cat.
ART. 19 A MIOCENE PORPOISE FEOM MARYLAND— KELLOGG 29
On the dorsal surface of the tubercle (fig. 10) near the antero-external corner and at the end of the groove that runs through it. Attached to a small triangular area near the apex of the manubrium was the fleshy process (the "triangular ligament" of the authors) of the mem-. Some of the threads of the fleshy process can be attached to the short narrow groove below the manubrium.
From the top of the long sacrum to the bottom of the body, the incus measures 3.2 mm. The ramus is slenderest at the posterior end of the symphysis, and the tooth row occupies about 65 percent of its total length. The upper edge of the mandible slopes from the coronoid process to the middle of the tooth row, while the lower edge is convex behind the end of the tooth row.
Although the right mandible is distorted by crushing, the angle appears to have extended posteriorly almost to the level of the condyle. The back of the tooth row and on the inner surface of the ramus. there is the usual opening for the large dental canal. With the exception of the distal ones, practically all teeth are in position on the left side of the rostrum and on the left.
The anterior tooth on each side is strongly elongated, inserted into the end of the premaxilla, and projects.
34 PROCEEDINGS OF THE NATIONAL MUSEUM VOL.69'
The neural spine is strong, thick at the base and is inclined backwards; the back face of the spine is. The shape of the neural canal and the proportions of the anterior articular facets cannot be determined at present. The postzygapophyses have almost horizontal articular surfaces and are located almost high on top of the neural canal.
The transverse processes are directed obliquely backwards and outwards and are much larger and longer than the corresponding processes of the atlas. There is a longitudinal carina on the inside of the shaft and corresponding depressions on each side. The zygapophyses and part of the neural arch are all that are visible on the right side.
Fifth Cervical.— In regard to thiclaiess, the centers of the fourth and fifth cervicals are about equal in size. There is a progressive decrease in the width of the interval separating the prezygapophyseal facets from the anterior to the posterior dorsal. These facets are nearly horizontal on the first seven dorsal sides, while those of the last three slope obliquely.
One each side of the center of the first the sixth dorsal, inclusive, below the level of the base of the neural.
ART. 19 A MIOCENE POEPOISE PROM MARYLAND KELLOGG 39
40 PKOCEEDINGS OF THE NATIONAL MUSEUM vol.CD. sionately larger and broader, the neural canal is lower, and the diapophyses are shorter. 14, no. 29) is longer than that of the fourth and is more conspicuously narrowed from side to side near the middle. The metapophyses are wider than on the preceding dorsals and the diapophyses are shorter.
Sixth dorsal.– The center is almost as long as it is wide and the. The neural spine is slightly wider anteroposteriorly. The mesial dorsoventral narrowing of the diapophyses has disappeared. six dorsals There are distinct facets on the posterosuperior lateral margins of the centra for the capitula of the following ribs, but these are not developed on the seventh and subsequent dorsals. 14, no. 31) is slightly longer than wide, clearly constricted near the center, and the apices of the metapophyses are directed upwards.
On the first seven dorsals the bases of the neural arches extend practically the full length of the centrum, but on the eighth, ninth and tenth dorsals they have receded from the posterior epiphysis. Eighth Dorsal.— There is no transitional dorsal with closely approximated facets for the tuberculum and capitulum of the corresponding rib on the side of the neural arch as in Eurhinodel'phis and many. However, on the eighth dorsal (pi.. 14, no. 32) of this fossil porpoise there is a single facet placed on the extremity of a short diapophysis.
The diapophyses project laterally from the neural arches at a considerably lower level than at the seventh dorsal.
ART. 10 A MIOCENE PORPOISE FEOM MARYLAND KELLOGG 41
All lumbar vertebrae are incomplete and none bears the transverse process on the right side. Of the anterior lumbars there are three that are more or less complete, and two others are represented by the left transverse process; these five lumbar vertebrae represent a consecutive series. All between these and the two that make up the end of the series have been lost.
The centra are all longer than wide and progressively decrease in length from the anterior one. Judging by the middle of the two anterior lumbars and the last lumbar, all have a more or less clear. The transverse processes are as long as the neural spines, very thin, and taper towards the distal end which is.
The transverse processes of the front loins are tilted forward and those of the hind loin backwards. The neural arches of the anterior loin are vertical, but those of the posterior loin slope forward. The epiphyses of the posterior lumbar are very slightly or not at all thicker than those of the anterior lumbar.
The lumbar part of this fossil porpoise has a more elongated center compared to that of Delphinodon dividuum, wider neural spines, larger metapophyses, and the transverse processes have ex-.
ART. 19 A MIOCENE PORPOISE FROM MARYLAND — KELLOGG 43
44 PEOCEEDINGS OF THE NATIONAL MUSEUM VOL. 69
ART. 19 A MIOCENE PORPOISE FROM MARYLAND — KELLOGG 45 The three anterior caudals of this fossil porpoise do not have their
The third caudal.-It (p. 10, fig.4) is complete except for the distal end of the neural spine and the extremities of the metapophys-. The minimum anteroposterior diameter (17.9 mm.) of the left transverse process is about two-thirds the diameter (29.8 mm.) at the margin. Judging by the center length and other features, this appears to be the sixth in the series.
The posterior facets for the chevrons are placed obliquely on the posterior faces of the great descending processes^. The metapophyses are large processes that have a lateral carina and they project forward beyond the level of the anterior epiphysis; their superior margins are at least 25.5 mm. The neural spine is wider than the neural arch, short in proportion to the size of the centrum, but longer than the transverse process, and with the limb squarely truncated.
The anteroposterior diameter (15.5 mm.) of the left transverse process at the narrowest point is about one-fifth that at the extremity (19.8 mm.); the distance from the canal at the base to the anteroexternal corner is 21 mm.
ART. 19 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 47
Above the dorsal opening of this vertebarterial canal is a short groove, but it does not extend upwards to the posterior edge of the neural arch. The distance between the dorsal and ventral opening of the lateral vertebral canal is 9 mm. Fourteenth caudal.— The posterior epiphysis (Fig. 13, Fig. 4) and neural spine are missing, but the vertebra is otherwise complete.
Thick plate-like descending processes bearing facets on the anterior and posterior ends of the chevrons extend the entire length of the lower surface of the centrum. The centrum is pierced dorsoventrally by a pair of large canals, the dorsal opening of which measures at least 5.8 mm. A pair of blunt processes develops on each side at the dorsal and ventral corners due to the mesial lateral constriction of the centrum, and they are oblique in direction to the transverse axis of the centrum.
ART. 19 A MIOCENE PORPOISE FROM MARYLAND KELLOGG 49
50 PROCEEDINGS OF THE NATIONAL MUSEUM
ART. 19 A MIOCENE POEPOISE FROM MARYLAND KELLOGG 51 Measurements of the right humerus (in millimeters)
52 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. GO
EXPLANATION OF PLATES
Distortion must be taken into account as this is a photograph of the image of the dorsal surface in the mirror back of the skull on the skeleton that is now one exhibit. 2, ninth dorsal, partly hidden by shafts of fifth, eighth and ninth ribs, and with repaired end of neural spine; Fig. 3, Tenth dorsal, partly hidden by the end of the ninth rib, and with the right transverse process and the end of the neural spine restored; Fig.
5, second lumbar, with extremity of neural spine and right transverse process restored; Fig.6, third lumbar, with centrum, right neurapophysis and right transverse process restored.
ART. 19 A MIOCENE PORPOISE FEOM MARYLAND KELLOGG 55
