GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 187 



in a tufaceous limestone. The tubes of the walls are solidly filled 

 with calcite. 



This was at first thought to be a smooth form of Balanus concavus 

 Bronn, but on cutting it the parietal tubes were found to be much 

 more numerous. In a specimen of B. concavus from the British Bed 

 Crag (Pliocene), No. 12058, U.S.N.M., there are 19 tubes in the 

 rostrum, which is 65 mm. long. Most of these tubes have transverse 

 septa at long, irregular intervals, but in some places near the edges 

 the septa are rather close, though irregular. 



The relation of this form to B. concavus can not be exactly esti- 

 mated until the opercular plates are found. It may be an ancestral 

 form of concavus or a distinct species. Meantime, it is readily recog- 

 nizable by the characters of the compartments. 



Locality and geologic occurrence. — Panama Canal Zone. From 

 85 foot cut, just on north side of big swamp, on relocated line Panama 

 Bailroad, 1£ to 2 miles beyond Camp Cotton toward Monte Lirio. 

 Gatun formation. Miocene series. D. F. MacDonald and T. W. 

 Vaughan collectors, 1911. 1 cluster; Cat. No. 324292, U.S.N.M. 



BALANUS (HESPERIBALANUS?), species. 



A small, conic barnacle having a basal diameter of about 7 or 8 

 mm. is represented by several compartments and one incomplete 

 specimen, without opercular valves. The walls are smooth except for 

 slight ripples parallel to the base. They are solid, having no parietal 

 tubes. The compartments are rather thick for so small a barnacle, 

 and when parted the articulating edges of the radii and the opposed 

 sutural surfaces are seen to be conspicuously crenulated. The basis 

 is calcareous, thin, and seems to have radial threads on its inner 

 face. 



These characters indicate a species of the subgenus Hesperibalanus, 

 or possibly Solidooalanus. Neither group has been recognized 

 hitherto in American tertiary deposits, or in the recent faunas of the 

 Panamic region or western Atlantic. The specimens do not seem 

 characteristic enough to serve as the basis of a new species, though 

 they can not, I think, be referred to any described form. 



Locality and geologic occurrence. — They were collected by Mac- 

 Donald and Vaughan in the " lowest f ossiliferous bed, the third below 

 the lowest limestone bed, Las Cascadas section, Gaillard Cut. Lower 

 part of upper half of Culebra formation. Oligocene." Station 6020<z, 

 Cat. No. 324295, U.S.N.M. 



A single valve was taken one-fourth mile south of Empire Bridge, 

 from lower dark clay beneath lower conglomerate, lower part of 

 Culebra formation, Oligocene; Station 6012a; Cat. No. 324296, 

 U.S.N.M. 



S370°— 18— Ball. 103 13 



