1912.] NATURAL SCIENCES OF PHILADELPHIA. 517 



1 teaks at the anterior T 4 T of the length, prominent; anterior end 

 rounded, posterior end wider, rounded in its lower half, obliquely 

 truncate above; basal margin evenly arcuate. The surface is 

 marked with unequal and mostly inconspicuous concentric wrinkles 

 and fine, close, radial threads, narrower than their intervals. 



Length 27, alt. 21, semidiam. 7.5 mm. 



Gatun Formation at the Spillway. 



A short, Tapes-like species with fine but distinct sculpture. On 

 the internal cast figured, the radial striae are obsolete towards the 

 two ends, but judging from an incomplete mould of the exterior, 

 the stria? extend undiminished nearly to the anterior end. The 

 interior is unknown. The shell was apparently quite thin. 

 Tellina aequiterminata n. sp. PI. XXVI. fig. 5. 



Known by a cast of the left valve, not differing much from T. 

 radiata in outline, but rather wider posteriorly and not twisted. 

 Beaks submedian; anterior end rather broadly rounded; posterior 

 end more tapering, but well rounded distally. The cast retains 

 vestiges of the external sculpture of concentric rather regular growth- 

 wrinkles. A low ridge indicates an impressed pallial line. The 

 capacious pallial sinus extends well beyond the beaks, and is appar- 

 ently confluent with the pallial line below, its upper line being well 

 arched. 



Length 44.5, alt. 24, diam. of left valve 5.5 mm. 



Gatun Formation at the Spillway. 

 Tellina (Eurytellina) vetula n. sp. Pi. XXVI, fig. 6. 



This species, known only by mutilated and imperfect remains, 

 is yet readily distinguishable by the sculpture of minute, crowded 

 concentric threads, narrower than their intervals, and about 12 

 to 15 in the space of 5 mm. in the lower half of the valve. 



There seems to be a rather emphatic radial sinuosity posteriorly; 

 the basal margin is well arched and the form rather broad. The 

 best-preserved example, which is imperfect anteriorly, has a length 

 of 43, alt, 29 mm. 



Pecten bed near Tower N, Culebra Cut. 

 Semele chipolana Dall. 



Trans. Wagner Free Inst. Sei,, III, p. 986, pi. 37, fig. 3. 



Pecten bed near Tower N. A nearly perfect mould of the left 

 valve, which agrees very well with Dall's account of this species 

 in shape and sculpture. The ample pallial sinus extends past the 

 middle of the valve. 



