2 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 67 



The Calvert formation of Maryland has yielded a rather large 

 number of porpoises and in the m^ain these species have their nearest 

 ajffinities with those in the Tortonian stage of Europe. A few of 

 them appear to have no counterparts in the European stages or at 

 least none have been described and one of these is ZarhacMs. With- 

 out entering into a discussion of the fauna as a whole, it is sufficient 

 to observe in the present connection that Zarhachis appears to 

 represent a highly specialized aberrant type whose family allocation 

 is more or less a matter of personal opinion in the light of available 

 data. If it is desirable to associate this porpoise with other genera, 

 it must be done with the understanding that it is merely a matter 

 of convenience. That ZarJiochis exhibits certain characters in com- 

 mon with Inia, Lipotes, and Platanista, there can be no doubt, but 

 whether they arose from one or three types of toothed whales can 

 not be demonstrated from the specimens now known. According 

 to our present knowledge, ZarhacMs represents a type which can 

 not be referred to any of the recognized families of toothed whales, 

 unless the limits of these families be redefined. A natural grouping 

 of some of the South American Miocene porpoises is not possible 

 at present because of the lack of adequate data on the construction 

 of their skulls. The ancestry of the ZarhacMs type of porpoise is 

 completely unknown at present. No fossil porpoises with this type 

 of skull have been described from the Miocene formations of Europe. 

 For this reason there can be little doubt but that it represents a 

 migrant from some other region, probably the south Atlantic, which 

 became associated with more widely distributed types during the 

 latter part of the Miocene period. 



The skull of ZarhacMs is modified in many ways, as will be noted in 

 the descriptive portions of this and the preceding paper. For the 

 purpose of bringing into stronger relief the characters of this porpoise, 

 it is necessary to compare them carefully with living river porpoises. 

 Tlie morphological characters involved in the construction of the 

 skull will form the main subject of this paper. 



ZARHACHIS FLAGELLATOR Cope 



Specimen. — -Cat. No. 10911, division of vertebrate paleontology. 

 United States National Museum. The brain case and the proximal 

 portion of the rostrum are represented; the lachyrmals, jugals, 

 periotics, tympanies, and bones of the inner ear are missing. Frag- 

 ments of three ribs were found near this skull. 



Locality. — The occurrence of this specimen is as follows: Near 

 latitude 38° 38' 45" N., and longitude 76° 32' W., on the western 

 shore of Chesapeake Bay, approximately 3^ miles south of Chesa- 

 peake Beach, Calvert County, Md. vShown on Patuxent quadrangle 

 or Patuxent foHo. No. 152. United States Geological Survey. 



