344 GEOGRAPHICAL AND GEOLOGICAL DISTRIBUTION. 



Americana has been applied. A peculiar form of porpoise, from 

 the Indian Ocean (?) and the Japanese coast, destitute of the dorsal 

 fin, has been described as Neomeris phocaeniformis. 



Of the remaining delphinoids the narwhal, or sea-unicorn (Mo- 

 nodon monoceros), inhabits the Arctic Ocean, rarely passing south 

 of the sixty-fifth parallel ; the beluga, or white whale (Delphinap- 

 terus leucas), closely related to the last, is also an inhabitant of the 

 Arctic Ocean, descending on the American coast to the St. Lawrence 

 River, and more rarely, in European waters, to the shores of Scot- 

 land. 



Excepting the Palaeocetus Sedgwicki, from the boulder clay of 

 Roswell Pit, Ely, England, whose remains were encased in a matrix 

 supposed to be Upper Jurassic (Kimmeridgian), the earliest ceta- 

 ceans of whose organisation we know anything are the zeuglodons, 

 which apparently represent a type intermediate between the toothed 

 and toothless forms of the present day. They occur in the Upper 

 Eocene deposits (Jacksonian) of the Southern United States; one 

 species (Zeuglodon Wanklyni) has also been discovered in the 

 equivalent Barton sands of England, and two, corresponding to the 

 American forms Z. macrospondylus and Z. brachyspondylus in 

 the deposits (Eocene or Oligocene) of Birket-el-Keroun, Egypt.* 

 Closely related in dental characters to the zeuglodons, but differing 

 in well-marked cranial features, are the squalodons, whose remains 

 are abundantly scattered throughout the Miocene and Pliocene de- 

 posits of many parts of continental and insular Europe (Vienna 

 Basin, France, Antwerp and Suffolk Crags, &c.). They have also 

 been noted from nearly contemporaneous strata in North America 

 (Squalodon Atlanticus, from Shiloh, New Jersey t) and Australia. 



The oldest known form of modern-type cetacean is Balaenoptera 

 Juddi, from the Oligocene (Headon) beds of the Hampshire basin, 

 England ; no other representative of an existing genus has thus far 

 been found to antedate the Miocene period. Bo.th the toothed and 



* Dames suggests that the two forms of Miiller may only represent the 

 male and female of a single species, which would then be the Zeuglodon 

 cetoides of Owen (" Sitzungsb. Berl. Ak.," 1883). 



t The forms described from the Eocene deposits of the Ashley River, South 

 Carolina, are considered by Van Beneden an.d Gervais to be only doubtfully 

 referable to this genus. 



