130 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 23 



of Lower California and Pliocene of Imperial County, California." 



— Hertlein & Strong, 1946, p. 58. Tres Marias Islands, Mexico, to 



Negritos, Peru. 

 Chlainys (Nodipecten) subnodosus (Sowerby). Bavay, 1936, p. 312. 

 Pecten nodosus inter?nedias [typ. err.; intermedius] Conrad. M. Smith, 



1944, p. 52. "Scammon's Lagoon, Lower California; Cape San 



Lucas (t3'pe locality) ; Ecuador." 

 Pecten nodosus subnodosus Sowerby. M. Smith, 1944, p. 52, fig. 692D. 



"Gulf of Tehuantepic [typ. err.; Tehuantepec], in 10-17 fathoms; 



near Cocos Island, in 66 fathoms. . . . Pecten digitatus Hinds 



(probably a young example)." [P. digitatus Hinds == Semipallium 



zeteki (Hertlein) ; see that species, this paper.] 

 Pecten (Lyropecten) subnodosus intermedius Conrad. Hertlein & 



Strong, 1946, p. 58. "Scammon Lagoon to Cape San Lucas, and 



the Gulf of California ; Clarion Island [Revilla Gigedo Islands, 



west Mexico]." 

 Lyropecten (Lyropecten) subnodosus (Sowerby, 1835). Keen, 1958, p. 



74, fig. 137. 

 Holotype: British Museum. 

 Type locality : La Plata Island, Ecuador. 



Original description : Pect. testa subaequivalvi, aequilaterali, auri- 

 culis inaequalibus; striis radiantibus numerosissimis, radiisque decem, 

 crassis, rotundatis, alternatim nodoso-vesicularibus vel subnodosis; intus 

 plerumque purpureo signata ; long. 5.25, lat. 2.75, alt. 5. poll. 



Additional description: Shell large and thick, averaging 130 mm in 

 height when adult, and usually longer than high ; left valve usually 

 more concave than right ; hinge line from almost half to slightly more 

 than half length of disk. Right valve often concentrically undulated; 10 

 ribs (occasionally 11), those next to submargins being almost obsolete; 

 ribs rounded and with 7 to 15 thin radial ridges; interspaces with 5 to 

 8 ridges of same size; fine concentric imbricating lamellae between all 

 ridges. Anterior auricle short for size of disk, of varying height, and 

 concentrically lamellose; from 8 to 12 radiating riblets, those next to 

 disk being much smaller ; byssal notch rather shallow and either rounded 

 or angled; ctenolium of 5 to 10 teeth in young shells, later only 3 or 

 4 obscurely present. Posterior auricle shorter, also lamellose, and with 

 10 to 18 radial riblets. Left valve often concentrically undulated; 

 usually 9 but occasionally 10 ribs, those next to submargin being almost 

 obsolete; ribs rounded and having 8 to 16 thin radial ridges; central rib 

 and alternate one or two either side often having hollow nodules, with 



