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Species / Macilentos Macilentus


Original Description of Rimella macilenta by White, 1889:

  • "Shell rather small, slender;the sides of the spire gently convex, each bearing about twelve abruptly raised longitudinal varices, which extend entirely across the exposed surface of the volutions in the direction of the axis of the shell, and are sometimes continuous from one volution to the next. The varices are separated by somewhat broad, concave spaces, and the entire surface is marked by fine, uniform revolving striæ, which are only a little less distinct upon the varices than upon the interspaces. The outer lip is moderately expanded, the expansion being a little greater anteriorly than posteriorly, rounded in front, thickened at its margin, which is continuous with the right wall of the posterial canal. The inner lip is somewhat thickly covered with callus, which extends backward and forms the left wall of the posterial canal. Anterior canal short, reflexed, and only slightly projecting beyond the anterior border of the outer lip. Posterior canal long, nearly inclosed by the approaching borders of its right and left walls, the two walls together forming a ridge, which is closely adherent to the spire, and, in fully adult examples, extends from the posterior angle of the aperture nearly or quite to the apex of the spire."

Locus typicus: About two 2 miles northward from New Indria, Fresno County, California, USA

Stratum typicum: Eocene

Rimella macilenta (White, 1889); Holotype; Coll. no. UCB 40142/33633; Photo Ron Voskuil

Macilentos macilentus (White, 1889); Paratype of Rimella macilenta White, 1889. 32,3 mm; LACM coll. no. 393.01, ex CAS 769; CAS locality 393: “Chico group about 2 miles northward from New Idria, Fresno County, California, USA where it was collected by Mr. Turner and myself.” (Clark & Palmer, 1923: 281, citing original description by White); Photo Ron Voskuil.

Rimella macilenta oregonensis Turner, 1938; Paratype; Coll. no. A662/33634; Photo Ron Voskuil

History and Synonymy


Rimella oregonensis Turner, 1938


Squires et al., 1992

Ectinochilus (Macilentos) macilentus oregonensis Turner, 1938

Specimens from institutionell collections

Ectinochilus (Macilentos) cf. macilentus; Baja California Sur, Mexico; Bateque Formation, Eocene; Coll. UNAM IGM 5169, Photo & Copyright Universidad Nacional Autónoma de México, Colección Nacional de Paleontología

Specimens from private collections:

Macilentos macilentus (White, 1889); Llajas Formation, Domengine Stage, upper lower Eocene; North side of Simi Valley, Santa Susana Mountains, Ventura County, southern California, USA; Collected by Richard Squires, 1979; Coll. Han Stoutjesdijk


  • Squires, R.L., Goedert, J.L. & Kaler, K.L. 1992. Paleontology and Stratigraphy of Eocene Rocks at Pulali Point, Jefferson County, Eastern Olympic Peninsula, Washington; Washington Division of Geology and Earth Resources Report of Investigations 31: i-iv, 1-27, Fulltext
  • Turner, F.E. 1938. Stratigraphy and Mollusca of the Eocene of western Oregon; Geological Society of America Special Paper 10, 130 p.
  • White, 1889

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