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Larcospira sp. Bjørklund et al., 1998

Description - Add description

Benson, 1966, p. 265-266; pl. 18, figs. 5-6:

Lithelius? sp.

Relatively small, elongate, ellipsoidal test, generally elliptical in outline but a few specimens almost diamond-shaped but with rounded corners; end views of test circular to subcircular or nearly elliptical in outline. Internal structure similar to that of Lithelius minor, i.e., 4-5 closely spaced, concentric, trizonal shells which appear as a single or double spiral in certain orientations; shells more closely spaced (6-12 µm) than in Lithelius minor and with a more elongate elliptical outline. Surface of test regular to slightly irregular, generally with thorns but without conical spines except for polar spines. Pores of each shell subcircular to subpolygonal, subequal, subregularly arranged, 8-15 on half the minor circumference of the outer shell. At one or both poles of the principal axis of most tests there is developed a portion of an outer shell, similar to the inner shells; in most specimens at one or both of these poles there is a group of 1-6 thin conical spines which are more or less parallel to the principal axis of the test and are of variable length (2-37 µm, generally 6-15 µm); the structures developed at each pole resemble, but do not represent, a pylome.

Measurements; based on 30 specimens from stations 27 and 71: major diameter (principal axis) of test 77-122 µm, minor diameter 62- 92 µm.

Remarks. Because this species has an internal structure similar to that of Lithelius minor, it was placed in the genus Lithelius. Both species, however, are not planispirally coiled; therefore, a new generic name should be proposed for them. Other species of the Family Litheliidae likewise may not be planispirally coiled. Restudy of all representatives of this family is needed before taxonomic revision is possible.
Except for the lack of a true pylome at one or both poles, the presence of larger pores, and their tests being ellipsoidal, not discoidal, specimens of this species from the Gulf resemble Stomatodiscus spiralis Dreyer (1889, p. 114, Pl. 10, fig. 63). Several specimens appear to be discoidal, but when rolled over under the microscope their ellipsoidal shape becomes apparent. Study of Dreyer's type material should be made before a new name is proposed for this taxon.

Distribution. This species has a rare but spotty distribution in the Gulf. It is present as far north as station 206; therefore, it is to some extent cosmopolitan. It is absent at stations 64, 90, 91, 92, 130, 133, 151, 194, 203, 208, and 214. Its distribution apparently is not influenced by upwelling. Its greater frequency in the southern half of the Gulf indicates its preference for more nearly oceanic water masses.
Benson 1866
Remarks. As noted by Benson (1966, p. 265), this species has an internal structure similar to that of Lithelius minor, i.e., four to five closely spaced, concentric, trizonal shells which appear as single or double spirals or as concentric shells, depending upon the orientation of the test. On the other hand, the genus Spongurus is more closely allied with species consisting of closely spaced, concentric ellipsoidal (not trizonal) shells such as Spongocore puella and Spongurus sp. cf. S. elliptica.
Benson 1983











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