N105

Bortyocyrtis scutum (Harting)

Haliomma scutum Harting, 1863, p. 11, pl. 1, fig. 18

Botryocyrtis scutum (Harting), Nigrini, 1967, p. 52, pl. 6, figs. 1a-1c

DESCRIPTION

"Cephalis tri- or quadrilobate: (1) heavy central lobe (A) directly over collar pores; (2) large lobe (B) on the dorsal side of A; (3) usually indistinct lobe (D) on the ventral side of A; and (4) in many specimens there appears to be a small, inconspicuous lobe (C) beneath and slightly lateral to B. Petrushevskaya (1964) figured this fourth lobe beneath and slightly lateral to lobe D, and in some specimens this appears to be so, but usually lobe C cannot be distingiushed either dorsally or ventrally. Possibly the spongy sheath surrounding the entire shell gives the illusion of a fourth lobe. There are 2 large pores at the base of lobe B, leading to the thoracic cavity. Details of the structure of lobes C and D could not be determined. All lobes with numerous small subcircular to subangular pores.

"Thorax short, lenticular in cross section, somewhat inflated, with relatively large subangular pores. Lumbar stricture not pronounced externally, but marked internally by a septal ring.

"In some specimens there is an abdomen, similar to the thorax, and then a fourth segment of varying length and having smaller pores. In other specimens, the "abdominal segment" is missing, and the small-pored segment adjoins the thorax. Mouth usually wide open or only slightly constricted, with a ragged termination.

"Entire shell surrounded by a sheath of spongy material. Particularly spongy specimens have a tubelike protuberance near the lumbar stricture (Petrushevskaya (1964) figured it near the collar stricture), but this feature is not constant, and, therefore, the species is not treated as a tubed Botryoid." (from Nigrini, 1967).

DIMENSIONS "Total length 81-128 microns. Maximum breadth 54-81 microns." (from Nigrini, 1967).

REMARKS

1. For a more complete synonymy and taxonomic discussion see Nigrini, 1967.

2. Benson's (1966) description, dimensions and detailed diagram of this species (Botryopyle sp. in Benson, p. 345) are consistent with the above. Benson's Botrycyrtis cf. caput-serpentis is not the same as B. scutum herein.

Plate 28, figures 1a,b

N106

RECENT DISTRIBUTION

1. Benson, 1966 (Botryopyle sp); "This species is very rare in the Gulf [of California] but is the most abundant of the four cannobotryd species present. It is generally confined to the southern part of the Gulf... It is, therefore, a species with greater affinity for oceanic than for Gulf waters."

2. Nigrini, 1967, fig. 28; "Indian Ocean occurrences - B. scutum is fairly abundant in low latitudes. South of 20 degreesS abundances decrease sharply to 1 percent to 2 percent of the described population, and south of 35 degrees S the species is practically absent. It appears to be a reliable and potentially useful member of the low latitude assemblage."

3. Nigrini, 1970, fig. 30; belongs to a tropical assemblage derived by recurrent group analysis of North Pacific samples, but the species does range as far north as 40 degrees N in the western and central Pacific.

4. Molina-Cruz, 1975, Code N19; used in factor analysis of southeast Pacific assemblages; cf. Appendix 10 for percent N19 at each station.