An Eocene volute gastropod from the Llajas Formation of southern California

This post focuses on a middle Eocene (about 48 million-years old) shallow-marine gastropod belonging to the family Volutidae. The term "volute" is a shortened term, referring to this family.

Eocene volutes are not that common in the coastal area of California, Oregon, and Washington. Locally, however, specimens can be found but usually require persistent collecting. An example of one of these volutes is a species of Lyrischapa from middle Eocene beds in southern California.

The scale in all the photographs has centimeter increments. The largest specimen shown below is 5.5 cm in height, but this specimen is somewhat incomplete.

All the views are of the back (abapertural) side of Lyrischapa lajollaensis (Hanna, 1927). These specimens show a growth series, from juvenile to adult size. The second largest  specimen has many boreholes made by boring algae or sponges. 

Front (apertural) views of Lyrischapa lajollaensis (Hanna, 1927): these are three of the same specimens (the second, fourth, and fifth ones) shown in the preceding image.

Genus Lyrischapa had wide distribution in the world during the Paleocene and Eocene, when warm-shallow seas were widespread.