The Only Cowrie Living On The West Coast of the United States

Neobernaya spadicea (Swainson, 1823) (the “chestnut” cowrie), a member of family Cypraeidae, lives today only from Monterey Bay, Monterey County, California to southern Baja California Sur, Mexico. Cowries are marine gastropods found most commonly throughout the world in warm to tropical, shallow-marine waters. There are approximately 260 living species and many extinct species. Living cowries are among the favorites of sea-sea collectors because the cowrie shell is glazed (highly polished) and can have an array of beautiful colors and patterns. The geologic record of cowries is from the Jurassic to Recent. There are many Cenozoic cowries in the fossil record of the west coast, and most of them lived during times that were much warmer than today in this area.

The cowrie now known as Neobernaya spadicea (Swainson, 1823) was misidentified as to genus [e.g., Cypraea], until 2000, when it was recognized as actually belonging to genus Neobernaya. The fossil record of N. spadicea is Pliocene to Recent.

The following four  images are of a specimen of N. spadices (49 mm length [distance between the posterior and anterior]; 29 mm width; and 24 mm height [distance between the base/bottom and the dorsum/top]. This specimen was collected in beach drift from a beach in Santa Barbara County, Southern California.

                                                         dorsal (dorsal)  view

                                                  ventral (base/bottom) view

  

                                right-side view (outer lip side)

                                  left-side view (inner lip side)

The name “spadicea” refers to the chestnut-brown color although there is a variation of the color of the top surface of the shell of this species: from chestnut brown to rust to red. The base (lower surface) and lower parts of its sides of the shell, however, is white.

This species lives in moderately cool waters, from intertidal to 50 m depth, especially the sublittoral zone near ledges and rocky areas. It lives in the near vicinity of forests of the giant kelp Macrocystis pyrifera, where this gastropod preys on bryozoans, hydroids, sponges, anemones, tunicates, and molluscan eggs. At least one of octopus apparently feeds on N. spadicea.

After hatching from eggs, the young of N. spadicea transition into a free swimming stage (veliger), but they are slow swimmers and many settle quickly to the ocean floor and begin to grow into adults. The juvenile stage of this species, like all cowries, is called the “bulla” stage. Its shell is very thin and elongate. Eventually, this stage will transition into the glazed over, strong shell of an adult. The maximum, full adult shell size is about 80 mm length.

Interior of a N. spadicea specimen showing the juvenile bulla stage. The entire specimen (length 46 mm, width 27 mm) was collected also as beach drift from a beach in Santa Barbara County, Southern California.

Much of the information used in this post is from the following very useful and up-to-date reference:

Groves, L.T. 2019. The family Cypraeidae Rafinesque, 1815, in the northeast Pacific: One spectacular species. Zoosymposia 13:131–138 (James H. McLean Memorial Volume).   

Septarian Nodules

 The name “septarian nodules” is derived from the Latin word “septum,” meaning seven, in reference to partitions dividing cavities. More specifically, the name refers to carbonate-rich nodules having an internal structure comprised of a series of carbonate-filled cracks or cavities, which separate polygonal blocks of hardened sedimentary material, such as mudstone.

The exterior of a septarian nodule, 13 cm tall and 11 cm wide. Utah.

Septarian nodules on the outside are not exactly eye-catching.

The interior of the same nodule, shown above. The interior of a septarian nodule can be, however, very interesting and eye-catching.

The nodules usually form early in the burial history of the muddy sediment before the rest of the sediment hardens into rock. Afterward, compaction causes cracks/cavities to form, and groundwater with dissolved minerals infills the cracks/cavities. Upon evaporation, the minerals crystallize out of the water. 

Septarian nodules, more accurately referred to as septarian concretions, have a smooth rounded exterior, which is normally gray. The mineral-filled cracks in the interior are typically yellow (calcite), but some also can be partially brown (aragonite = another carbonate mineral).

This septarian nodule (12 cm wide and 15 cm tall) was cut (slabbed) in order to show the intricacy of the infilled cavities.

Lastly, I included this slabbed (cut) septarian nodule because it is a nice specimen and one that was used in one of my previous posts (July 17, 2014) entitled "Pseudofossils."The rounded and smooth exterior of most of the septarian nodules have been mistakenly by some collectors as “dinosaur eggs,” which they are NOT! Pseudofossils are inorganic objects.

Rock hounds commonly cut the septarian nodules in half and polish them. They can sell for low to high prices, depending on the complexity of the radiating crack pattern and the variety of the coloration.