PANAMIC-PACIFIC PELECYPODA 121 



Scolimytilns (Aeidlmytilns) adamslanus (Dunker) Plate 12. figure 5; 



Plate 13, figures 4, 4a, 6 



Mytilus adamsiana Dunker, 1856, Proc. Zool. Soc. London, vol. 24, p. 360. (issued May, 

 8, 1857). Panama.— Reeve, 1858, Conch. Icon., vol. 10, Mytilus, pi. XI, fig. 55. 



Brachidonies (Hormomya) adamsianus (Dunker), Hertlein and Strong, 1946, Zoologica, 

 vol. 31, pt. 2, pp. 70, 71. 



Hormomya adamsiana (Dunker), Soot-Ryen, 1955, Allan Hancock Pacific Expeditions, 

 vol. 20, No. 1, pp. 37-40, pi. 3, fig. 11, text-figs. 22, 25, 31. 



The shell is small (length to about 16.5 mm.), generally narrow and 

 elongate, the umbonal ridge high, angled and vaulted, the ventral side 

 flattened or impressed. The beaks are small and nearly terminal in position. 

 The dorsal side of the umbonal ridge is coarsely sculptured with large 

 radial ribs, few in number near the beak but increase by forking or addition 

 distally and on the successive growth disks, each setoff by a shelf 

 or a deep resting mark; ribs on the ventral side much smaller. Color 

 of surface is some shade of purple on the dorsal side and white on the 

 ventral side. Dorsal or hinge margin crenulated above the scar of the liga- 

 ment. 



Length 15.6 mm.; height 9.3 mm.; diameter 6.6 mm. 



Punta Banda, Lower California, Mexico. Mr. T. Burch. 



Length 15.2 mm.; height 8 mm.; diameter 8 mm. 



Jipijapa (Puerto Callo), Ecuador. 



Range — Lower California to Ecuador. Panama: Panama (Dunker). 

 Ecuador: Santa Elena; Puerto Callo (this is the port of Jipijapa, the 

 Xipijapa of Cuming). 



Scolimytilns (Aeidimytilus) puntarenensis (Pilsbry and Lowe) 



Plate 13, figures 5, 5a 



Mytilus (Hormomya) puntarenensis Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. 



Philadelphia, vol. 84, p. 104, pi. 10, fig. 6 Puntarenas, Costa Rica (Lowe). 

 Brachidontes Puntarenensis (Pilsbry and Lowe), Soot-Ryen, 1955, Allan Hancock Pacific 



Expeditions, vol. 20, No. 1, pp. 46, 47, pi. 3, fig. 14; text-fig. 29. 



Shell small (length from 10 to about 18 mm.), generally broadly 

 modoliform, high or wide posteriorly, narrower anteriorly, the small beaks 

 much pinched and placed at the extreme end, and when perfect, the umbonal 

 region bearing several nepionic caps, of which the first is extremely small 

 and smooth, the others with ribbed sculpture. The ventral side is flattened 

 to deeply impressed, the umbonal slope running prominently from the 

 beaks to the posterior-ventral corner and rises as a high, rounded or subangu- 

 lated ridge; some specimens are almost as long as high. The sculpture is 

 costate, formed by small, radial riblets divided generally into two sets by 

 the umbonal ridge, those on the dorsal side being larger, neatly granulated 

 and quite uniform, the others below the umbonal ridge much finer and 

 smoother. Anterior margin below the beak has a large external rib or ridge 

 which passes into the hinge and forms there a large, knoblike tooth. Ex- 

 ternal color a uniform dark-brown or deep purple, heaviest over the pos- 

 terior-dorsal slope grading into a lighter shade or white on the ventral side. 



Length 17 mm.; height 8 mm.; diameter 8.7 mm. (Type, Puntarenas, 

 Costa Rica, ANSP 155629). Length 11.7 mm.; height 9 mm.; diameter 8 

 mm. Punta Carnero, Santa Elena, Ecuador. 



