84 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL, 20 



leaves a small scar above the adductor. There are traces of siphonal re- 

 tractor muscles in the middle of the valve and the siphons are long, even 

 the branchial one, with the septum ending below^ the branchial siphon in 

 three branched flaps. 



The umbones are incurved ; the margin above the ligament and just 

 behind it is finely, transversely striated. 



Fig. 66, Solamen columbianum (Dall). Off Pyramid Cove, San 

 Clemente Island, California. Placement of adductor 

 muscles. 



Fig. 67. Solamen columbianum (Dall). Off Santa Rosa Island, 

 California. The strong cylindrical foot with apical in- 

 flated part, relatively strong anterior retractors and very 

 weak posterior retractors. 



Fig. 68. Solamen columbianum (Dall). Off Santa Rosa Island, 

 California. Posterior part seen from behind. Fine papillae 

 on the upper part of the mantle margin which terminates 

 in a heartshaped flap below the anal opening. 



Fig. 69. Crenella deoussata (Montagu). EI Segundo, California. 

 Foot with posterior retractor and adductor. 



Fig. 70. Botula fusca (Gmelin). 4 miles N. of Isla Tortuga, 

 Venezuela. Muscle scars. Anterior and posterior adduc- 

 tors are rather large, anterior retractor placed on the 

 anterior margin beyond the umbo, posterior retractor very 

 small and placed above the adductor. Indistinct scars in 

 the middle are formed by the retractors of the siphons. 



Fig. 71. Botula fusca (Gmelin). 4 miles N. of Isla Tortuga, 

 Venezuela. The separated anal and branchial siphons are 

 of nearly equal length. 



Fig. 72. Botula fusca (Gmelin). 4 miles N. of Isla Tortuga, 

 Venezuela. Branchial siphon in posteroventral view show- 

 ing the three branched flaps on the septum. 



Fig. 73. Adula californiensis (Philippi). Cape Arago, Coos County, 

 California. Muscle scars with the scars for the siphon 

 retractors below the posterior adductor. 



Fig. 74. Adula californiensis (Philippi). Cape Arago, Coos County, 

 California. Posterior part of the mantle with the anal 

 siphon and the papillae on the branchial part. 



Fig. 75. Adula diegensis (Dall). Bodega Lagoon, Sonoma County, 

 California. Posterior part of the mantle with the anal 

 siphon and the papillae on the branchial part. 



Fig. 76. Ad'ula diegensis (Dall). Bodega Lagoon, Sonoma County, 

 California. Posterior part seen from behind. 



Fig. 77. Lithophaga {Labis) aftenuata (Deshayes). Puerto San 

 Bartolome, Baja California. Placement of muscle scars. 



Fig. 78. Lithophaga (Diberus) canalifera (Hanley). Bahia de 

 Manta, Ecuador, a. Side view with the projecting incrusta- 

 tion, b. Dorsal view of the specimen with the incrustation 

 on the left valve. 



