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Cycladophora cornutoides (Petrushevskaya, 1967)

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Cycladophora davisiana var. cornutoides

First segment of shell small , its surface often rough. Second and third segments fused, their boundary thus indistinguishable. Pores disposed in regular transverse rows. At widest part of shell (third segment?) there are 12-13 pores in one transverse row, i. e., more than in the foregoing variant. Specimens with distinct fourth segment could not be distinguished, but in several shells sharp expansion below noted, probably beginning of formation of fourth segment. Internal skeleton as slender as in typical variant. External extensions of needles A, Vert, Lr and Ll long; on needles D, Lr and Ll there are often lateral processes (Figure 70, I).
Dimensions: length of first segment 15- 20μ , width 20-25μ, length of following part of shell up to 100μ and more, width of shell at point where third segment should originate 55-65μ, width of shell below, where expansion corresponding to fourth segment begins, 80μ (and probably more).
Location. Found in our material in deepwater sediments of Indian and Pacific Ocean sectors of Antarctic; shells constitute about 1% of total number.
Note. This variant differs from the foregoing in the greater expansion of the bottom of the shell, and also in the larger number of smaller pores. At the same time it is similar to the typical variant (particularly to the specimens drawn in Figure 69, IV) in that the shell does not narrow below but expands. Judging from his description, Riedel (1958) encountered both typical forms of C. davisiana, and also the two variants described above in his material, although he did not distinguish between them. However, the features according to which these forms are differentiated (nature of wall of first segment, different degrees of development of external extensions of needles A, Vert, D, Lr and Ll, demarcation or fusion of second and third segments, etc.) are sufficiently constant to distinguish the variants. C. davisiana var. cornutoides resembles somewhat Halycaliptra cornuta from the northwestern part of the Pacific Ocean (Bailey (1866) in the outline of the shell, particularly the specimen drawn by the author in Figure 14, Table L, but differs from that species in its larger dimensions.
Petrushevskaya 1967
Cycladophora davisiana var. cornutoides

C. davisiana var. cornutoides, is composed of three segments with indications of initiation of a fourth segment on some specimens. The boundary between the second and third segment is almost indistinguishable with the third segment gradually expanding towards its base. Besides these features, distal extensions of its internal skeleton in the form of spines and lateral processes, some as large as 40 Ám, are characteristic of this subspecies (Plate I, 6-10).
Morley 1980











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