510 



PROCEEDINGS OF THE ACADEMY OF 



[Dec, 



On the last half of the last whorl the ribs become smaller; the con- 

 cave intervals do not extend be- 

 low the periphery and are rounded 

 at their lower ends. 



Length 2, diam. 0.6 mm. 



Excavation at Gatun Locks. 



Turbonilla (Chemnitzia) sratunensis n. sp. 

 Text fig. 46, c. 



The shell is minute, rather rap- 

 idly tapering, the diameter at the 

 last whorl about double that of 

 the first post-embryonic whorl. 

 Embryonic shell bulimoid, of about 

 2 whorls, the last very globose, 

 pjg 4 nearly half immersed. Post-em- 



bryonic whorls 5^, convex, the 

 greatest convexity just above the suture, which is deeply impressed. 

 Sculpture of rounded, slightly protractive, axial ribs, equal to their 

 intervals, 14 on the last whorl; the concave intervals gradually 

 effaced at the periphery of the last whorl. 



Length 1.7, diam. 0.65 mm. Length of embryonic shell 0.3, 

 diam. 0.2 mm. 

 Excavation at Gatun Locks. 



Related to T. bartschiana, but more rapidly tapering, with the 

 whorls more swollen below and the riblets noticeably protractive. 



Area dalli n. sp. PL XXIII, fig. 4. 



A small, very obese ark, with beaks at the anterior fourth of 

 the length, full and well incurved; hinge-line rather short. Valves 

 equal, similarly sculptured with about 28 ribs wider than their 

 intervals, those of the median and anterior part strongly and closely 

 tuberculate, as in Area chiriquiensis Gabb, the posterior ribs nearly 

 smooth. Interior unknown. 



Length 20, alt. 16, diam. 15.7 mm. 



From a lignitic clay at the bottom of the Culebra Cut, near Tower 

 N; a bed below the Pecten bed at the same place. 



Pecten (Euvola) reliquus n. sp. PI. XXIV, fig. 3. 



• Pecten sp. (vielleicht n. sp.) " Toula, Jahrb. k.k. Geol. Reichsanst., 1908, 

 LVIII, p. 755, text figs, 12, 13. 



The left valve is strongly convex, the right almost flat, being 

 very gently convex towards the beaks, concave on each side of the 

 middle. Sculpture of about 24 strong ribs. In the left valve they 



