1918] Barrows: Skeletal Variations in the Genus Peridinium 



431 



Perfectly definite examples of a form attributed to P. granii have 

 been found in collections in which the ventral plate pattern of Meta- 

 peridinium is combined with the dorsally left oblique asymmetrical 

 pattern ; and similar specimens, presumably of a* form of P. granii 

 also, have been taken from Union Bay, Alaska, showing the dorsally 

 right oblique asymmetrical pattern. 



Orthoperidinium. — In the subgenus, Orthoperic^nium, the fol- 

 lowing species are found with the primary dorsal plate pattern, shown 

 in fig. 5 : 



P. oceanicum Van H. 



(Stein, 1883, pi. 10, fig. 1) 

 P. claudicans Paulsen 



(pi. 3, figs. 1 and 2) 

 P. depressum Bail. 



(Broch, 1910, p. 51, fig. 26) 

 P. parallelwni Broch 



(Broch, 1906, p. 153, fig. 4) 



P. conicum (Gran) O. and S. 



(Paulsen, 1908, p. 59, fig. 74) 

 (Gran, 1902, p. 189, fig. 14) 



P. oitusum Karsten 



(Faure-Fremiet, 1908, p. 223, 

 fig. 9) 



Forms presenting the ventral plate pattern of Orthoperidinium 

 and the secondary dorsal plate pattern shown in fig. 6 are : 



P. tahulatum Ehrenberg 



(Entz, 1904, fig. 7, a, b) 

 (Schilling, 1892, pi. 3, figs. 21a, 



b) 

 P. hipes Stein 



(Stein, 1883, pi. 11, figs. 7 



and 8) 

 (Schilling, 1891, pi. 3, figs. 

 23a, b) 

 P. leonis Pav. 



(Pavillard, 1916, p. 33, fig. 6) 

 P. pentagonum Gran 



(Gran, 1902, p. 191, fig. 15) 

 (Paulsen, 1908, p. 59, fig. 76) 

 P. anthonyii F. F. 



(Faure-Fremiet, 1908, p. 216, 

 fig. 3) 



P. typus Bergli 



(Faure-Fremiet, 1908, p. 222, 

 fig. 8) 

 P. cinctum Ehrenberg 



(Baehmann, 1911, pi. 6, fig. 7) 

 P. conicoides Pauls. 



(Paulsen, 1905, p. 1, fig. 2) 

 P. faeroense Pauls. 



(Paulsen, 1905, p. 5, fig. 5) 

 P. obtusum Karsten 



(Karsten, 1906, pi. 23, figs'. 

 12b, e) 

 P. subinermis Pauls. 



(Paulsen, 1907, p. 19, fig. 26) 

 P. willei Huitf.-Kaas., (fresh- 

 water) 



(Schilling, 1913, p. 45, fig. 0) 

 P. westii Lemm. (freshwater) 



(Schilling, 1913, p. 47, fig. 0) 



Only one example has been found in literature in which the ven- 

 tral plate pattern of Orthoperidinium has been combined with that 

 of an asymmetrical dorsal plate pattern, in this case that termed the 

 right oblique. This appears in P. punctulatum Pauls. (Paulsen, 

 1907, p. 19, fig. 28). This combination has also been found by the 

 writer in a collection from Sausalito, California, in a specimen which 



