Spondylus echinatus is a delightfully spined thorny oyster widely ranging across the Indo-West Pacific, south of Amami Islands, Japan. It is a very variable species in terms of spine development and colouration, which has resulted in a number of synonyms being given. A very famous one is Spondylus castus Reeve, 1856 and it is often still referred to as that, since it is listed in many books under that name. The brown shelled and white spined form as shown has been known as Spondylus albibarbatus Reeve, 1856. Both Anton, 1838 and Chenu, 1844 gave it the name Spondylus albus, but both are synonyms. Furthermore, a densely spinous form was given the name Spondylus spectrum Reeve, 1856. The juvenile shell is characteristically white with small black patches. A filter-feeding bivalve which lives a sessile lifestyle with the right valve attached on hard substrates, it is a common species found from low intertidal zone down to about -20m deep. Typical shell length around 90mm., very large specimens may exceed 130mm. Spondylus zonalis Lamarck, 1819 was traditionally considered to be a form of this species, but is now considered to be a separate full species in its own right.

Spondylus albibarbatus Reeve, 1856 SH: 9cm. This resembles S. spinosus, but radial ribs more numerous, with dense strong spines. Okinawa, southward to tropical West Pacific, rocky bottom, within 20m deep.

Cebu Island, Central Visayas, Philippines