. Bulletin of the British Museum (Natural History), Geology. 2l8 KIMMERIDGIAN DINOFLAGELLATES & ACRITARCHS Leptodinium cf. crassinervum (Deflandre) Sarjeant, 1969 Plate 3, figure 8, plate 5, figures 4-6; text-figure 19 Description : The shell is broadly ovoidal to polygonal in shape. The cyst wall is thick (c. 2-5jjl) and densely granular. The crests are membraneous in character and arise from slight thickenings of the periphragm; although they are low, they are quite obvious. They give rise to occasional short spines, up to c. 4-4-5[i. in height. Tabulation: 4', la, 6", 6c, 6'",
. Bulletin of the British Museum (Natural History), Geology. 2l8 KIMMERIDGIAN DINOFLAGELLATES & ACRITARCHS Leptodinium cf. crassinervum (Deflandre) Sarjeant, 1969 Plate 3, figure 8, plate 5, figures 4-6; text-figure 19 Description : The shell is broadly ovoidal to polygonal in shape. The cyst wall is thick (c. 2-5jjl) and densely granular. The crests are membraneous in character and arise from slight thickenings of the periphragm; although they are low, they are quite obvious. They give rise to occasional short spines, up to c. 4-4-5[i. in height. Tabulation: 4', la, 6", 6c, 6'", ip, ipv, i"" and 2s. Plate i' is elongate, extending down almost two-thirds of the epitract. Plates 2', 3' and 4' are more or less equal in size. The precingular plates are relatively large, except plate 6" which is reduced because of the large anterior intercalary plate (la). The six postcingular plates are of variable shape and size: plate 2'" is reduced to accommodate the intercalary plate (ip) which is rather large. Plate i"' is quite small; the other postcingular plates are relatively large, plate 4"' being the largest of all the plates. A crescent- shaped posterior ventral plate, ipv, separates the sulcal plates from the single antapical plate. The cingulum is moderately narrow, formed by six plates (plate 6c is very small); it is slightly spiral, laevorotatory and divides the theca unequally: the epitract is twice as large as the hypotract. The sulcus is short and broad; its posterior portion is formed by two sulcal plates, one small, the second quite Fig. 19. Leptodinium cf. crassinervum (Deflandre). Tabulation and archaeopyle forma- tion: left, in ventral view; right, in dorsal view. Specimen BM(NH) slide (i). X Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the o
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