COMPLETE GRAU : PECTINIDAE OF THE EASTERN PACIFIC 49 



Propeamussium (Cyclopecten) vitreum gelatinosurn (Mabille y Roche- 



brune). Carcelles, 1950, p. 76, pi. 4, fig. 73. "Region magallanica 



y Sur de Patagonia." 

 Palliorum \Palliolum\ (Delectopecten) macrocheiricola Habe, 1951, 



p. 80. "New name for Delectopecten vitrea Hiro, 1938, Ann. Zool. 

 Japon., vol. 17, p. 474 [actually given as Pseudamussium (Palliolum) 



vitreum (Gmelin) by Hiro], non Gmelin, 1791." 

 Delectopecten vitrea (Gmelin). Kuroda & Habe, 1952, p. 19. Pacific 



Ocean: -0° to 35° N; Japan Sea: to 46° N. 

 \non\ Delectopecten zacae Hertlein. Hertlein & Emerson, 1953, p. 350, 



pi. 27, figs. 7, 10, 16. ". . . 110-200 fathoms off the east slope of 



Clipperton Island." [670 miles SW of Acapulco, Mexico. = 



Pecten vitreus Gmelin.] 

 Holotype: ? 



Type locality : Unknown. 



Original description (Gmelin) : O. testa hyalina margine acuta: 

 radiis tenuissimis, squamularum arcubus concentricis. 



Chemn. Conch. 7, t. 67, f. 637, a. 



/8) Chemn. Conch. 7, t. 67, f. 637, b, c. 

 Habitat in Oceano Septentrionali, inter fucos et zoophyta, lentis ut 

 plurimum magnitudine, testa levi fragili alba. (B) albo rubroque varia 

 auricula altera emarginata spinosa. 



Additional description : Shell small, averaging 20 inm in height and 

 length, moderately to deeply convex and nearly transparent; hinge line 

 % to % length of disk; anterior auricles slightly longer than posterior. 

 Both valves ornamented with concentric rows of small vesicles, a minute 

 ridge connecting them horizontally; rows of vesicles continue to hinge 

 margin, covering posterior auricle of right valve and both auricles of 

 left ; when broken ofif, scales leave minute semicircular ridges, and these, 

 together with connecting ridges, result in a continuous scalloped ridge. 

 Anterior auricles of right valve with 5 to 8 concentrically lamellated 

 radial riblets, a sharply angled, rather narrow byssal sinus, and a ctenoli- 

 um of 3 to 6 teeth. Surface of both valves (except anterior auricle of 

 right) covered with very minute and irregular radial striae. 



Remarks: Despite its very wide distribution, this species is quite 

 constant in form. Variable features are the distribution and profusion 

 of the vesicles and the convexity of the valves, the latter often being 

 also slightly oblique. Japanese specimens dilTer somewhat, being smaller, 

 less convex, and less profusely ornamented, some also having low con- 

 centric undulations of the disk just below the umbo. 



