NORTH AMERICAN 1A.TER TERTIARY AND QUATERNARY BRYOZOA. 143 



Family SMITTINIDAE Levinsen, 1909. 



Genus SMITTINA Norman, 1903. 



(For description see Bulletin 106, U. S. National Museum, p. 456.) 



SMITTINA TRISPINOSA Johnslon, 1838. 



Plate 22, figs. 7-14. 



1838. Lepralia tmpinosa Johnston, History of British Zoophytes, p. 324, pi. 57, fig. 7. 



1889. Smittia trispinosa Jelly, A synonymic catalogue of marine Bryozoa, p. 252 (general bibliog- 

 raphy). 



1894. Smittia trispinosa Levinsen, Zoologica Danica (Danske Dyr), Heft 9, p. 70, pi. 6, figs. 10, 11. 



1896. Smittia trispinosa Nevu.ni, Briozoi PostpUocenici di Spilinga (Calabria), Atti Accademia 

 Gioenia di Scienze Naturali in Catania, ser. 4, vol. 9, p. 41, fig. 22. 



1899. Smittia trispinosa Waters, Bryozoa from Maderia, Journal Pvoyal Microscopical Society, p. 16. 



1900. Smittia trispinosa Robertson, Papers from the Harriman Alaskan Expedition, VI, The 



Bryozoa, Proceedings Washington Aacademy Sciences, vol. 2, p. 327. 

 1902. Smittia trispinosa Calvet, Bryozoaires marins de la region de Cette, Travaux de I'lnstitut de 



Zoologie de ilontpellier, Mem. 11, p. 56. 

 1902. Smittia trispinosa Calvet, Bryozoaires marins des cotes de Corse, Travaux de I'lnstitut de 



Zoologie de Montpellier, Mem. 12, p. 30. 



1907. Smittina trispinosa Nordgaard, Bryozoen von dem norwegiseheu Fischereidampfer "Michael 



Sars," Bergens Museums Aarbog, no. 2, p. 15. 



1908. Smittia trispinosa Robertson, The incrusting cheilostomatous Bryozoa of the west coast of 



North America, University of California Publications, Zoology, vol. 4, pi. 22, figs. 68-70. 

 1910. Smittia trispinosa Osbdrn, Bryozoa of the Woods Hole region. Bulletin Bureau of Fisheries, 



vol. 30, p. 246, pi. 27, fig. 65 (American bibliography). 

 1912. Smittina trispinosa Nordgaard, Revision av Universitets museets samUng av norske 



Bryozoer, Kgl. norske Videnskabers Selskabs Skriften, no. 3, p. 22. 

 1914. Smittina trispinosa Osburn, The Bryozoa of the Tortugas Islands, Florida, Publications of 



the Carnegie Institution of Washington, no. 182, p. 208. 



Variations. — This species is extremely variable and many varieties are known. 

 The varieties arborea Levinsen and lamellosa Smitt appear to be peculiar to the 

 boreal regions. The varieties munita Hincks, himucronata Hincks, nitida "Verril, 

 japonica Ortmann, etc., have no particular geographic extension and they generally 

 accompany the type. The varieties, of which we have not cited the bibliography, 

 are established either on the zoarial aspect or on the form of the avicularian man- 

 dibles; that is to say, on very secondary characters. Calvet, 1902, has sho\vn 

 that these characters themselves are rather characters of variations. 



The detailed study of the variations would be desirable and would permit 

 perhaps the discovery of the cause of them, which would be very important from 

 the biologic point of view. It is probable that the richness of the waters in plank- 

 tonic elements, the swiftness of the currents, the nature of the substratum, the 

 agitation of the waters, and tlie nature of the bottom are the causes of the varia- 

 tions of which it is important to establish exact limits. 



The geographic distribution of this species is universal; it has been discovered 

 in all the explored seas. According to the known rules, the geological distribution 

 must be correlative. But it is not so; only Waters and Neviani have mentioned 

 fossil specimens. 



The constant characteristic of this species is its very regular mode of gemma- 

 tion (fig. 10) operating alternately between the walls which are absolutely recti- 



