Batten, Roger Lyman.2005-10-062005-10-061984http://hdl.handle.net/2246/525313 p. : ill. ; 26 cm.Includes bibliographical references (p. 12-13)."The principal shell layers of Neomphalus fretterae McLean, 1981, are an inner concentric crossed-lamellar and an outer complex crossed-lamellar layer. The protoconch is unusual in being composed of four layers rather than one or two as in most other gastropods. The narrow, high-angled crossed-lamellae of the inner principal layer are nearly identical with those of advanced mesogastropods, rather than the broader, low-angled archeogastropod crossed-lamellae. This, along with shell shape, ornament, and the presence of a muscle platform suggests a closer relationship with the mesogastropod limpets than with the archeogastropods. Muscle attachment is by direct muscle fiber insertion, forming tubules in the shell, and also by myo-adhesive epithelial cells which may form a myostracal layer. Based on the multiple layers found in the protoconch, I speculate on the possibility that the larval stage may have remained planktonic for an extended period"--P. [1].4796347 bytesapplication/pdfen-USQL1 .A436 no.2776, 1984Neomphalus fretterae.Limpets -- Pacific Ocean -- Anatomy.Limpets -- Galapagos Islands -- Anatomy.Limpets -- Anatomy.Mollusks -- Pacific Ocean -- Anatomy.Mollusks -- Galapagos Islands -- Anatomy.Mollusks -- Anatomy.Living fossils.text