) 



STAURONEIS. l6l 



Var amphicephala (S. amphicephala Kutz. ; H.V.H. Atl. pi. 4., fig. 

 6 and 7* ; in Type 67) ; plate 1, fig. 57 



Valve with parallel margins, apices abruptly attenuate-rostrate-capitate. 



These two varieties are found mixed with the type form, from which it 

 changes completely. 



B. Valves with tri-undulate margins. 



S. Smithii Grun. (Ueber neue etc., i860, p. 564; S. linearis, 

 W. Sm., S.B.D. i., p. 60, pi. 19, f. 193 ; H.V.H. Atl., pi. 4, f. 10* ; Type No. 

 45); plate 1, fig. 58. 



Valve oblong lanceolate-triundulate, with apices apiculate, sub-acute, 

 showing a lumen ; stauros rather narrow, slightly dilated at its extremities ; 

 raphe surrounded by a narrow hyaline zone ; striae delicate, about 30 in 1 

 c.d.m. ; frustules united in bands by several individuals together. Length, 2 

 to 3 c.d.m. 



Fresh water Here and there, always in small quantities. Belgium, England, Scotland, France. 



S. Legumen Ehr. (Mikr., pi. xxxix., 3, f. 104 ; h.v.h. Atl., pi. 4, 



f. 11*), plate 1, fig. 59. 



Valve linear with three equal undulations, apices rostrate, a little capitate, 

 showing a lumen ; stauros rather broad, not dilated at the extremities ; raphe 

 surrounded by a narrow hyaline zone; striae very delicate, about 28 in 1 

 c.d.m. Frustules in bands of several individuals together. Length about 

 3 c.d.m. 



Freshwater Antwerp (rare). England (Kitton), Scotland (Greg.). 



This is probably only a narrow elongated form of the preceding. 



77. Raphe oblique, sub -sigmoid. 

 S. obliqua Greg. ! (q.j.m.s., 1866, p. 10, pi. 1, f. 35*), plate 25, 



fig. 703. 



Valves sub-rhomboid oblong or rhombojdal lanceolate, with apices sub- 

 acute or sub-obtuse ; raphe oblique, sub-sigmoid ; stauros enlarged infinitesi- 

 mally up to the margins of the valve ; striae transverse, 20 to 22 in 1 c.d.m., 

 rather strongly punctate, forming longitudinal undulate lines. Length of 

 valve about 4 c.d.m. Breadth, 1*5 c.d.m. 



Marine. Scotland, Ireland (Gregory !) 



Several species of Stanroneis of English authors do not belong to this 



genus, such as St. dubia Greg. I which is Achnanthes Hungarica Grun. ! ; St. 



ovalis Greg. ! which is Achnanthes ovalis {Greg.) H. V.H. ; St.dilatata W. Sm. 



which is Navicula crucicula IV. Sm. ; St. punctata W.Sm. which is Navicula 



punctata W. Sm. 



M 



