Conus weltoni

Conus weltoni (Hickman, 1980)

Descrizione e caratteristiche:

Conus n. sp. A Voices, 1945 (checklist) in Warren and others, 1945, U.S. Geol. Surv. Oil and Gas Invest. Prelim. Map 42.

Description.

Shell of medium size for genus, slender, with relatively high, turreted, beaded spire; shoulder concave, with moderately deep anal notch; aperture narrow and of uniform width; body whorl convex posteriorly, becoming concave anteriorly with a pronounced constriction of the anterior end; periphery ornamented by 20 to 23 nodes that are obliquely produced onto the body whorl following growth lines; body whorl ornamented by faint spiral sculpture that is strongest anteriorly; shoulder lacking spiral sculpture; shell thin and delicate for its size; spiral angle 50°; apex abraded on all available specimens.

Etymology. — The species is named for Bruce Welton, who collected and donated the holotype.

Dimensions of holotype. — Height 40.0 mm; maximum diameter 18.1 mm.

Material examined. — 48 specimens.

Stratigraphic distribution. — Conus weltoni Is restricted to the lower member of the Keasey Formation. It has been recognized as part of the fauna from the type section of the formation on Rock Creek for many years and has been referred to as "Conus n. sp." or "Conus n. sp. A" (Durham, 1944; Vokes in Warren and others, 1945; Warren and Norbisrath, 1946). Specimens are abundant at many localities and invariably occur in association with Bathyhembix columbiana. Preservation is generally poor at weathered outcrops, with a predominance of chalky Internal molds at most localities ⁽¹⁾.

Conus weltoni occurs in beds of early Keasey age on the Wlllapa River at Holcomb, Washington, where it also is associated with Bathybem,bix columbiana⁽¹⁾.

Holotype. — VSNM 251433.

Figured paratypes. — VSNM 251434, 251435.

Unfigured paratype. — USNM 251436 (Height 28.8 mm, USGS 25026).

Type locality. — Lower member, Keasey Formation: USGS 25025⁽¹⁾. – Late Eocene to Early Oligocene. In terms of the molluscan faunas, the Keasey fauna is clearly delimited from that of the upper Eocene Cowlitz formation and much more closely allied to that of the higher Oligocene horizons of Oregon and Washington ⁽²⁾.

Other localities. — Lower member, Keasey Formation: USGS 15306, 15307, 15308, 15309, 15263, 15265, 25026, 25027, SU Schenck Loc. 435. Beds at Holcomb, Washington: UCMP A1810 ⁽¹⁾.

Comparison. — The characters that seem to be most useful in separating the Paleogene species of Conus with turreted beaded spires are the number of nodes per whorl, shape of the nodes, presence or absence of spiral sculpture on the shoulder, presence or absence of sculpture on the posterior portion of the body whorl, and body whorl profile. The height of the spire seems to be a variable character in most species ⁽¹⁾.

C. vaderensis (Weaver and Palmer, 1922) and C. cowlitzensis (Weaver, 1912), from the Cowlitz Formation in southwestern Washington, both have more prominent spiral ornamentation over the entire body whorl as well as spiral sculpture on the shoulder ⁽¹⁾.

C. aegilops (Anderson and Hanna, 1925), from the type Tejon Formation in California, has squarish nodes that are truncated anteriorly, in contrast to the obliquely produced nodes on the new species ⁽¹⁾.

Likewise in C. schencki (Weaver and Kleinpell, 1963), from the middle member of the Gaviota Formation, the nodes are not obliquely produced. The shoulder is also relatively broader and the spiral angle wider (65°) ⁽¹⁾.