6 PROCEEDINGS OF THE ISrATIONAL MUSEUM. vol. 63, 



vertcbrarterial canals pierce the neurapophyses and in addition 

 there are foramina for the spinal nerves. Ten dorsal and at least 

 four lumbar vertebrae are present. As a whole the vertebral column 

 bears a closer resemblance to Platcmista than to any other living 

 porpoise. The neural spines are deep, flattened, and rather squarely 

 truncated on their upper extremities. The transverse processes of 

 anterior caudals are set in elliptical depressions. The posterior 

 caudals are perforated dorso-ventrally by paired arterial canals. The 

 first seven pairs of ribs have capitula articulating with the centra as 

 Avell as tubercula articulating with the transverse processes. The 

 three posterior ribs articulate with the transverse process. The first 

 three pairs of ribs are compressed and their necks are bent at right 

 angles to the shafts. The eighth, ninth, and tenth ribs lack necks. 

 The sternum resembles that of Platanista and differs from that of 

 Inia in the absence of vertical conical processes behind the articular 

 facets for the first ribs. 



Remains of river porpoises are relatively rare in the Calvert Cliffs, 

 and only one skull and associated skeleton have been obtained. A 

 few imperfect vertebrae which apparently belong to the same type of 

 cetacean have been examined by the writer, but these specimens do not 

 warrant description. Judging by the relative quantity of remains 

 of fossil cetaceans which have been assembled in institutions to 

 which acknowledgments have been given, the family Platanistidae 

 seems to have been outnumbered by long and short beaked dolphins 

 as well as by whalebone whales during the deposition of the Calvert 

 formation in the Chesapeake embayment. 



Specimen. — Cat. No. 10485, Division of Vertebrate Palaeontology, 

 United States National Museum. The skeleton of this fossil porpoise 

 is incomplete. It includes a nearly complete skull. The rostrum 

 is entire and the preservation is excellent, but most of the posterior 

 end of the cranium, with the exception of the bones which form the 

 vertex, was missing when the skull was collected. The lachrymal^ 

 and jugals are missing and the right pterygoids are imperfectly 

 preserved. The periotic and the two tympanic bones found with 

 the skull are all imperfect or broken. Both lower jaws are pre- 

 served, though they are badly crushed in the region of the coronoid. 

 The sternum is incomplete. The hyoid bones are perfect and entire. 

 One cervical, ten dorsal, four lumbar and three posterior caudal 

 vertebrae, as well as four chevron bones, were found associated with 

 the skull. Sixteen ribs and eighteen bones of the paddle also be- 

 long to this specimen. 



Locality. — The occurrence of the specimen is as follows : Near lati- 

 tude 38° 40' 30" North and longitude 76° 32' West, on the western shore 

 of Chesapeake Bay, approximately one mile south (1,610 meters) of 



