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Phormospyris tricostata Haeckel, 1887

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Benson, 1966, p.334-336; pl. 23, fig. 9:

Phormospyris tricostata Haeckel

Phormospyris tricostata Haeckel, 1887, Challenger Rept., Zool., Vol. 18, p.1087, Pl. 83, fig. 15.

Bilocular cephalis, with scattered short thorns or spines and small, unequal, circular to elliptical pores; separated from a truncate-conical thorax by a collar stricture. Pores of the thorax similar to those of the cephalis. Sagittal ring asymmetrical, with a straight, vertical apical bar which extends as a thin, conical to three-bladed apical spine; ring three-bladed in section except for a short cylindrical median bar. A conical vertica1 spine or thorn present. Six collar pores present; as in Desmospyris anthocyrtoides the jugular pores covered by a small, dorsal, sagittal cephalic lobe. The dorsal and primary lateral bars extend as ribs in the wall of the thorax and terminate as three-bladed to conical spines or feet projecting downward from the thoracic margin; thorax slightly lobate between the three thoracic ribs. The primary lateral bars as well as the secondary lateral bars also extend as and are collinear with short conical spines which arise from the collar stricture. A few accessory terminal spines extend from the margin of the thorax in most specimens.

Measurements; based on 5 specimens from station 71 and 106: sagittal height of cephalis 37-49 Ám, maximum breadth 79-96 Ám; length of thorax 49-90 Ám, maximum breadth 86-96 Ám; length of apical spine 5-12 Ám, of vertical spine 2-15 Ám, of terminal foot-like spines 12-37 Ám.

Remarks. Haeckel (1887, p. 1087, Pl. 83, fig. 15) neither described nor illustrated the small dorsal sagittal cephalic lobe of Phormospyris tricostata. This structure, however, is visible only in certain orientations; therefore, Haeckel may have overlooked it. Haeckel's illustration shows a broader conical thorax than that of the Gulf species, but this is a variable character. Other than these differences the Gulf species and P. tricostata Haeckel are identical.

Distribution. This species is very rare in the Gulf. It occurs only at stations 71, 81, 92, 106, 115, 133, and 136; therefore, it is a rare member of the southern Gulf oceanic assemblage. Its occurrence north of station 92 may indicate that it responds to the upwelling there but its generally rare occurrence makes analysis of this impossible.
Haeckel (1887, p. 1087) reported this species from the central Pacific at "Challengerö station 272. It has not been reported from high latitudes; therefore, it is probably a tropical species.
Benson 1966


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