OBSERVATIONS ON LIVING SOLENOMYA. 



273 



opening with papillae about it and these quite unlike the long 

 pointed papillae of the siphonated lamellibranchs or even the 

 truncate papillae of Saxicava, though morphologically they are 

 the same. On viewing this region 

 from above the papillae appear bunched 

 together or spread apart, the result 

 of the sudden dilatation or partial 

 contraction of the opening. 



The sides of the siphonal opening 

 are in constant motion in and out, 

 though this motion is alternate and 

 rhythmic. The proboscidiform foot 

 swings from one side to the other 

 within the shell, like an elephant's 

 trunk and this motion may be related 

 to the alternate siphonal movements; 

 this correlation, however, was not ob- 

 served. 



Just below the siphonal opening a 

 slight depression is seen on the mantle 



on each side connected by a transverse depression forming a 

 symmetrical figure. Stempell shows a marking of the same 

 nature in S. togata in the form of an angle with the apex down- 

 ward. 



A view of the animal as it rests in the usual position on its 

 back with valves widely apart will reveal the attitude and 

 behavior of the palpi (Fig. 15). Cutting the ventral membrane 

 will give a clearer view of these parts. The palpi are adherent 

 for a short distance to the side of the foot but are free beyond, 

 and extend backward and downward. These organs are long, 

 slender, semi-tubular with ends much larger and the whole 

 structure delicate and diaphanous. No line or angularity in 

 section indicates in any way that this semi-tubular appendage 

 has come about by the adhesion of two palpi. The palpi of 

 other lamellibranchs are more or less triangular in shape with 

 their upper edges partly united. In Solenomya velum, the long 

 tube-like appendages encircle the base of the foot with their 

 dilated extremities resting directly on the compact sides of the 



B 



FIG. 15. Anterior end from 

 below: .4, anterior adductor 

 muscle; B, branchia; F, foot! 

 P, palp-appendages resting on 

 branchia. 



