Figure 2: The byssal opening A , when present, can be seen as an opening on the underside of the sand can vary greatly in size. This Tridacna crocea shas a very large byssal opening. Also labeled is the upper margin B as seen from the underside of the s., through the byssal opening. The margin of this s .Giant Clams. All 9 species of the Family Tridacnidae are included in Appendix II of CITES. Tridacna gigas; Tridacna derasa; Tridacna squamosa; Tridacna maxima; Tridacna crocea; Tridacna rosewateri; Tridacna tevoroa; Hippopus hippopus; Hippopus porcell 6. Giant Clams. While there may be some trade in meat for .Crocea Clam Guide, Tridacna crocea information, clam facts and pictures. Marine aquarium care for the Crocus Clam, where to find giant clams, and tridacnid propagation. Boring Clam, Saffron Colored Giant Clam..