Benson 1966 - Tristylospiris scaphipes

Bilocular cephalis smooth, cardioid, with pores of variable size but generally small, one-half to two times the width of the bars, circular to subcircular; pores aligned on either side of sagittal ring larger, circular to elliptical, about three pairs each on the dorsal, upper, and ventral sides, the lower pair on the dorsal and ventral faces larger than the others. Sagittal ring occupies sagittal stricture, three-bladed with two of the blades extending laterally inward, the third extending outward in the sagittal plane, ovate to D-shaped, with a short, cylindrical median bar. Collar ring with four collar pores (text-fig. 8A), a pair of larger, subtrapezoidal cardinal pores and a pair of smaller, subtriangular cervical pores; latero-ventral corners of collar ring marked by angular corners raised slightly from the basal surface of the cephalis. Primary lateral bars extend as very short, thin, conical spines; a short axial thorn present. Three divergent downward, three-bladed feet arise from the collar ring, two lateral feet originating from the primary lateral bars, one dorsal foot corresponding to the dorsal spine. Jugular pores absent; secondary lateral bars represented by raised ribs extending laterally along the bases of the lateral blades of the dorsal foot. Individual blades of the feet slightly bifurcated distally giving them blunt terminations. Feet of variable but equal length. Short, thin, conical apical and vertical spines extend from and are collinear with the straight apical and vertical bars of the ring, respectively; in most specimens these spines barely visible.A few specimens observed with a thin, irregular, small-pored lattice developed between the three feet, but a true thorax absent.

Measurements: based on 30 specimens from station 92: sagittal height of cephalis 42-60 m, maximum breadth 70-118 µm; length of feet 13-63 µm.

Remarks: Haeckel's description and illustration of Tristylospiris scaphipes Haeckel (1887, p. 1033, Pl. 84, fig. 13) differ from the majority of the Gulf specimens only in the absence of the apical spine and in the presence of slightly spatulate termination of the feet. Because these features are subject to variation, the Gulf species is identified with Haeckel's species. The distinguishing features of this species are the smooth, small-pored bilocular cephalis and the equal three-bladed feet.

Distribution: This species is rare but cosmopolitan in the Gulf. It is absent at station 194 and those to the north. It is common at station 192 and nearly so at station 191.Both of these stations are located within the northern diatomite facies. The frequency of this species is also slightly greater at other stations located within the diatomite facies, but the percentage of its occurrence is too low to state definitely that it responds to upwelling. Its frequency in the southern Gulf is slightly less than in the northern half of the Gulf. Its frequency is much lower at marginal stations, thus indicating its preference for offshore or mere nearly oceanic waters. Haeckel (1887, p. 244) reported this species from the northwestern part of the Pacific at Challenger station 244, about 35 degrees N. latitude. It has not been reported from high latitudes thus may be confined to tropical and temperate regions. \ From: Benson, 1966, p. 316-318; pl. 22, figs. 7-10; text-fig. 8A:Tristylospiris scaphipes HaeckelTristylospiris scaphipes Haeckel, 1887, Challenger Rept., Zool., vol. 18, p. 1033, Pl. 84, fig. 13.

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