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Fourth Contribution to the Marine Fauna of the Miocene Period of the
By E. D. Cope.
(Read before the American Philosophical Society, April 5, 1895.)
The three preceding “Contributions” appeared in the Proceedings of the Academy of Natural Sciences of Philadelphia for the years 1867, 1868 and 1869 respectively. Their subject matter is almost exclusively confined to the description of the remains of Cetacea which occur in the marine deposits of middle Neocene age of the Atlantic coastal region, and more exactly, in the Yorktown formation of Dana, or the Chesapeake formation of Darton and Dall. The present paper continues the description of these forms preliminary to an illustrated memoir on the subject. The word “marine” has been introduced into the title to distinguish the series from the numerous papers which have appeared on the paleontology of the lacustrine neocenes of the West. For the sake of uniformity the term Miocene is retained.
PARACETU3 MEDIATLANTICUS, sp. nov.
The genus Paracetus has been recently proposed by Lydekker* to include members of this family which possess a well-developed series of teeth in the (?) premaxillary and maxillary bones. It is up to the present time represented by one species, the Paracetus pouchetii Moreno, of the Santa Cruz bed of eastern Patagonia, of the district of Chubut. The present species is apparently not distantly related to that one.
This genus stands near to Cogia Gray, and can scarcely, with present information, be referred to a distinct family. The presence of superior teeth cannot alone be regarded as necessitating this course, as they occasionally occur in Cogia. Thus in C. sima Owen, from the coast of India, there are two teeth at the anterior extremity of the upper jaw, and a male of a rather small species preserved in the U. S. National Museum from the eastern coast of the United States exhibits the same character.t A male in the Museum of the Wistar Institute of the University of Pennsylvaniat from the coast of New Jersey at Sea Isle City, has no teeth in the upper jaw. The genus Paracetus seems to me to be only distinguishable from Cogia by the posterior extension of the tooth series to the posterior
Anales del Musen de la Plata : Paleontologia Argentina; II: Cetacean Skulls from Patagonia, p. 8, Plate iii.
# For the opportunity of examining this specimen I am indebted to Dr. Goode, Director of the Museum.
My thanks are due to Prof. Horace Jayne, Director of the Wistar Institute, for the opportunity of studying this specimen.
part of the maxillary bone. Perhaps when the skeleton is known other characters will be detected.
The name of this genus is stated by Dr. Lydekker in the text of his description to be as I have cited, but the name Hypocetus stands at the top of the paragraph in which this statement is made, and is also attached to the plate in which it is figured. I have followed Dr. Lydekker's expressed intention rather than what may be a lapsus calumi or other mis. take.
Char. specif - As the posterior border of the skull and the extremity of the muzzle of the specimen are broken off, an exact idea of its outline cannot be given. However, the form was probably much as in the P. pouchetii, and more elongate than in the species of Cogia. This form is subtriangular, with the basal border convex, and the two lateral ones slightly concave. The muzzle is probably, however, produced into a ros. trum, as the maxillary borders are parallel at the point where it is broken off. On the right side, where the maxillary bone is best preserved, there are eight alveoli; the teeth are lost. The lateral border of the maxillary bone overhangs the tooth line considerably in front, and spreads away from it outwards and backwards in a gradually thinner edge to the deep notch which bounds the supraorbital region anteriorly. The rise of the anterior border of the facial basin is within this notch, and not without it, as in the species of Cogia ; and is gradual, attaining a considerable elevation immediately in front of the temporal fossa, and a little within the vertical plane of the supraorbital border. The premaxillary bones are separated by the deep vomerine channel which they partially overroof on each side, and are separated posteriorly by the prenarial part of the vomer posteriorly. The latter forms an elevated crest directed forwards and unsymmetrically to tbe right. The premaxillaries spread gradually outwards posteriorly to a thin margin, and are concave opposite to the vomerine crest which separates them, that of the left hand descending to the nareal orifice. The skull is broken off at the blow-holes, so that it is difficult to affirm positively whether the right blow-hole existed or not. It was apparently present, but smaller and posterior in position to the right one. The inferior surface of the maxillaries slopes upwards and outwards, leaving the inferior face of the vomer quite prominent below. The vomer forms the half of a circle in transverse section above, and extends as far anteriorly as the specimen extends.
There is a large supraorbital foramen between the preorbital notch and the rising edge of the facial crest, as in the sperm whale; and there is a smaller one in a direct line posterior to it just exterior to a more elevated part of the crest, within a line above the posterior part of the supraorbital border. A longitudinal groove anterior to the supraorbital foramen is pierced in its fundus by two foramina. Anterior to the groove a depressed foramen pierces the maxillary bone near the premaxillary border. Anterior and interior to the corresponding foramen of the left side a depressed foramen pierces the premaxillary bone. This foramen is absent from
the right side. In the other hand the right premaxillary is pierced near the anterior part of the vomerine crest by a large round foramen, which is wanting from the left side. A large foramen erces the inner side of the lateral crest half-way to the superior border, and opposite the middle of the left blow-hole.
The dental alveoli are subround, and are separated by narrow septa. They are not deep, the deepest equaling 50 mm., so that the teeth have been easily lost.
Length of fragment on middle line..
.800 Width of skull at supraorbital notch ; left side restored... .800 Width of muzzle where broken off....
.100 Width of left premaxillary at vomerine keel.
.170 Elevation of lateral crest above orbit (apex broken off).....310 Length of series of eight teeth......
From Drum Point, Chesapeake Bay, Maryland.
Ziphiinæ Flower ; Ziphiidæ Gill (Ziphius preoccupied).
Char. gen.-Allied to Choneziphius, but the solid rostrum of the vomer bifurcates posteriorly and embraces a basin which takes the place of the maxillary basin of the right side, and reduces that of the left side to very small dimensions. Blow-holes very unsymmetrical, the left only preserved in the specimen.
This genus has certain characters which ally it to the Physeteridæ. The internareal part of the vomer is directed very obliquely upwards to the left, and then forwards to the left on the superior surface for a distance, when it turns to the right as in Paracetus and Cogia. Instead of terminating at this point as in those genera, it assumes the swollen form and dense structure seen in the species of Choneziphius, and besides send. ing forwards the usual rostrum on the median line, it continues to the right, and apparently spreads out into a thin plate which forms the floor of a wide basin, and which apparently continues to and forms its right border, overlying the posterior plate of the maxillary. This basin is represented in Puracetus mediatlanticus by a longitudinal shallow concavity of the right side of the superior keel of the vomer, which is a rudiment as compared with the basin in the present genus. The rostrum of the vomer extends to the narrow extremity of the specimen, where it is broken off. The fracture exhibits no tube or channel.
PROC. AMER. PHILOS. Soc. XXXIV. 147. R. PRINTED MAY 29, 1895.