PANAMIC-PACIFIC PELECYPODA 4Sl 



Jouannetia (Pholadopsis) pectinata (Conrad) Plate 80, figures 3, 3a 



'Pholadopsis pectinata Conrad, 1849, Proc. Acad. Nat. Sci. Philadelphia, vol. 4, p. 156 



Baja California and Peru. — Conrad, 1850, Jour. Acad. Nat. Sci. Philadelphia, 



vol. 1, p. 279, pi. 39, fig. 3. 

 Triomphalia pulcherrima Sowerby, 1849, Thes. Conch., vol. 2, pt. 10, p. 501, pi. 106, figs. 



58, 59 in soft rock at low water. West Colombia. — Sowerby, 1850, Proc. Zool. 



Soc. London for 1849, p. 161, pi. 5, figs. 2a-d. 

 Jouannetia {Triomphalia) pectinata (Conrad), Hertlein and Strong, 1950, Zoologica, 



vol. 35, No. 19, p. 248. 

 Jouannetia {Pholadopsia) pectinata (Conrad), Turner, 1955, Johnsonia, vol. 3, No. 



34, pp. 137, 138, pi. 83. 



Adult shell large (length about 50 mm.), bullet or pearshaped, inequl- 

 valve, white, thin. Young shells are nearly equivalve, beaked posteriorly and 

 have the anterior gap uncovered. In the adult, the valves become strongly 

 unequal and the anterior gap is covered by a large paired callum. Posterior 

 end of each valve is wedge or tongue-shaped, that of the right valve longer 

 and sharply serrated on the sides. 



A small, bullet-shaped Pholadopsis is common along the coast west 

 of Manta, Ecuador, boring into shale rocks. These forms are probably small 

 specimens of J. pectinata but good examples are difficult to extract. None 

 have been available for close examination and figuring in the present study. 



Range — Lower California to northern Peru. Ecuador: Manta, 



Subfamily XYLOPHAGINAE 



Valves like those of Teredo with the anterior gap open at all stages of 

 growth. Borers in wood but not forming a calcareous tube. 



Genus XYLOPHAGA Turton, 1822 

 (Xylotomea Dall, 1898). 



Type species by monotypy, X. dorsalis Turton. Norway. 



Shell like that of Teredo but with a double protoplax and without 

 internal apophyses. The united valves form a globular shell, each with a 

 median furrow, the anterior side widely gaping, not covered by a callum, 

 the valves closed behind. No siphonoplax or calcareous tube, the animal 

 contained within its shell, except for the slender, contractile siphons. Borers 

 in wood. 



Xylophaga mexlcana Dall Plate 80, figure 4 



Xylophaga mexicana Dall, 1908, Bull. Mus. Comp. Zool., vol. 43, No. 63, p. 425. "Off 

 Acapuico, Mexico in 141 fathoms". — Turner, 1955, Johnsonia, vol. 3, No. 34, pp. 

 150-152, pi. 90, fig. 1, 2. 



Shell small (length 5 mm.), beaked and widely gaping in front, rounded 

 and closed behind. Beak large, sculptured with numerous, finely denticulated, 

 concentric ridges. The umbonal-ventral sulcus is narrow and deep, bordered 

 by a small ridge on the posterior side. 



This species is known only from a dead specimen dredged off Acapuico. 

 Lacking the dorsal plate, its affinities with other forms cannot be determined. 

 It appears to be related to X. globosa Sowerby, 1834, described from Chile. 



Range — Mexico. Mexico: Acapuico. 



Family TEREDINIDAE 

 Wood borers. The two piece or bivalved shell is much reduced in size, 



