42 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



twisted, with the lunule bent inward, at least in large specimens, and 

 furnished with radiating furrows which form the teeth. Generally there 

 is a single strong tooth more or less furrowed ; but the teeth seem to be 

 so variable that it is nearly impossible to give an adequate description of 

 them. The margins are crenulated, with especially strong crenulations 

 behind the ligament. The crenulations on the posterior margins are ex- 

 tremely variable. 



The color of the interior is either whitish-gray or dark purplish, some- 

 times lighter anteriorly. The crenulations on the posterior margin are 

 very fine on the dark-colored shells, while on the light-colored they are 

 very often formed by the external ribs only. The number and form of 

 the tentacles and papillae on the posterior mantle margin vary also, the 

 tentacles being sometimes simple, sometimes digitate, with smaller papillae 

 in between. All characters vary so much that a large amount of material 

 will be needed to be able to decide if there is more than one species or not. 

 The form with nearly smooth posterior part of the valves, named S. bifiir- 

 caius obsoletus by Dall, 1916, is found mixed with more heavily ribbed 

 forms and seems not to be of subspecific value. 

 Occurrence: Usually intertidal, fastened to rocks. 



Distribution: From Crescent City, California (42° N), south to Cabo 

 San Lucas, Baja California. (One sample is labelled "Peru," but this is 

 certainly wrong.) 



Septifer zeteki Hertlein and Strong 1946 

 Plate 4, fig. 21 ; text-fig. 34 



Septifer zeteki Hertlein and Strong, Zoologica, vol. 31, 1946, p. 71, 



PI. 1, figs. 1-2. 

 Syn.: Septifer cumingii Recluz 1849. 



Mytilus cumin ffianus Reeve 1858. 

 Holotype: California Academy of Sciences. Paleo. Type Coll. 

 Type loc: Isla Taboga, Panama; 25 fms. 



Remarks: Recluz (1849) described <S. cumingi from "les cotes de I'ile 

 Annaa (pres le detroit de Panama), dans I'Ocean-Pacifique." Reeve 

 (1858) records M. cumingianus from Panama. Carpenter (1855) says 

 that this species, which he reports from Mazatlan, is extremely rare and 

 closely resembles the young of S. bilocularis. He also mentions the "granu- 

 losa ribs, with rather long bristly hairs rising up between." Morch 

 (1860) reports this species from Puntarenas, Costa Rica. Smith (1885) 

 says: "The small shells described by Recluz as Septifer cumingii should 

 not, I think, be separated from this species [5. bilocularis]" and remarks 



