90 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 20 



margins like the smooth species. Two typical specimens in the collec- 

 tions are labelled Bahia de la Independencia, Peru, and if correct, extend 

 the distribution very far south. 

 Occurrence: Boring in clay or soft shale. 

 Distribution: Coos Bay, Oregon, to San Diego, California. Peru? 



Adula soleniformis (Orbigny) 1846 



Mytilus soleniformis Orbigny, Voyage dans I'Amerique Meridionale, 



vol. 5, Mollusques, 1846, p. 649, PI. 85, figs. 17-18. 

 Holotype: ? 



Type loc: Neighborhood of Payta, Peru. 



Remarks: This species, which is the type of the genus Adula, has the 

 anterior retractor slightly before the umbones ; a definite keel ; and fine 

 radiating lines on the anterior side and before the keel, very strong and 

 riblike on the lunule. The anterior margin is thickened and crenulated ; 

 the ventral margin is smooth ; the posterior margin is finely striated from 

 the keel to the posterodorsal corner, where the surface is devoid of 

 striation ; the dorsal margin has strong, toothlike crenulations from be- 

 hind the ligament to the posterodorsal corner. The resilial ridge and 

 the nymphae are weak. The muscle scars were not observed (specimen 

 examined, U. S. National Museum, Cat. no. 128635). 

 Occurrence: This species seems to be rather rare and apparently known 

 only from the type locality. The habitat is unknown. 

 Distribution: Peru. 



Adula calif orniensis (Philippi) 1847 

 Plate 9, fig. 50 ; text-figs. 73-74 



Modiola calif orniensis Philippi, Ztschr. f. Malakozool., vol. 4, 1847, 



p. 113. 

 Syn.: Adula sty Una Carpenter 1864. 

 Holotype: ? 



Type loc: Vancouver Island, British Columbia, Canada. 

 Remarks: Shell smooth, usually without radiating sculpture, sometimes 

 with faint traces on the lunule. Anterior margin crenulated at least 

 dorsally, and occasionally with obscure crenulations behind the ligament. 

 Posterodorsal triangle with a filthy incrustation. Posterior third of shell 

 not distinctly higher than anterior third. Byssus strong, in tufts from 

 a main laterally compressed stem. The dorsal siphon with smooth mar- 

 gins and the margins of the ventral siphon furnished with irregular 

 papillae. 



