186 BULLETIN" 103, UNITED STATES NATIONAL MUSEUM. 



than wide, exactly as in the type of B. glyptopoma. There are 16 

 tubes in the rostrum of one of the specimens figured (fig. 2). The 

 basis is profusely porous, the pores septate (fig. 3, left hand and 

 midd]e individuals of group shown in fig. 1). The middle specimen 

 of this group is 31 mm. high, the rostro-carnial diameter about 

 22 mm. 



B. glyptopoma was described as a subspecies of B. concavus Bronn, 

 but it differs from that by the closely septate parietal tubes, and is 

 evidently a distinct species. In B. concavus the tubes are filled up 

 near the summits, and are open, with very few septa below, or none 

 in the American subspecies. The Miocene form formerly referred to 

 B. glyptopoma is a distinct subspecies of B. concavus. 



Location and geologic occurrence. — The specimens are from Sta- 

 tion 5903, across Chagres River and about 200 to 225 feet above it, 

 top of hill opposite Alhahuela, in a gray tufaceous limestone, Cat. 

 No. 324298, U.S.N.M. and Station 5906a, 50 to 75 feet below 5905, 

 Cat. No. 324299, U.S.N.M. Both collected by D. F. MacDonald. 

 Upon mentioning to Dr. William H. Dall that I had identified a 

 Pliocene barnacle from these Stations, he kindly informed me that 

 " both are above the Oligocene strata and separated from the latter 

 by an unconformity. They are doubtless Pliocene. 5906a is the 

 lower of the two horizons." 



Mexico. From the Sayula District of Chiapas, on the Arroyo 

 Chapapoapam. Pliocene series. Dr. C. W. Hayes and others, col- 

 lectors; 1911. Station 5886. One specimen, without opercular valves. 

 Cat. No. 324291, U.S.N.M. 



BALANUS CONCAVUS RARISEPTATUS, new subspecies. 



Plate 67, fig. 4. 



In form this barnacle is somewhat cylindric with contracted sum- 

 mit in the adult stage, convexly conic when young. The orifice is 

 ovate. The walls are only slightly roughened longitudinally. The 

 carinolateral compartments are narrow, the parietes about one-third 

 as wide as the lateral compartments. The radii are wide with 

 oblique summits, without pores; the articulating edges being crenu- 

 lated. The parietal tubes have very few, irregularly scattered, trans- 

 verse septa. There are 29 tubes in the rostrum of the type-specimen. 

 Another, of equal size, has 17 tubes in the lateral, 6 in the carino- 

 lateral compartment. 



Length, 27 mm. ; carino-rostral diameter, 22.5 mm. ; lateral diame- 

 ter, 21 mm. In the largest individual exposed the rostrum is 35 mm. 

 long. 



This form is represented by a group of about 16 individuals grow- 

 ing upon and largely concealing a single old one of about 37 mm. 

 basal diameter. Probably three generations are present. They were 



