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BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



species became extinct in this area. 1 It appears that two phyletic 

 series are represented, strongly differentiated from their first appear- 

 ance, and both differing from any European forms known to me. In 

 the glyptopoma series the scutum is narrower, more strongly sculp- 

 tured than European concavus. In the proteus series it is wider, 

 more delicately sculptured. The sequence of known forms is about 

 as follows: 



BALANUS CONCAVUS GLYPTOPOMA, new subspecies. 



Plate 21, figs. 2, 3; plate 22, figs. 2-2c. 



In the Yorktown, Virginia, Miocene there is a rugged, small-ribbed 

 form (pi. 21, fig. 3) resembling the typical B. balanus superficially, 

 and reaching a diameter of about 25 mm. There are fully 20 pores 

 in the rostrum. The opercular valves resemble those of the following 

 form, which may fairly be considered a direct descendant. 



The typical B. c. glyptopoma of the Caloosahatchie Pliocene (pi. 21, 

 fig. 2 ; pi. 22, figs. 2-2c) has rather numerous small ribs on the parie- 

 tes, sometimes weak or nearly obsolete, and not stronger toward 

 the apices. The orifice is large, the summits of the radii not very 

 oblique. Carinorostral diameter 20 to 37 mm. The scutum is 

 sculptured with strong growth-ridges cut into high, erect nodes by 

 the rather deep longitudinal striae. This sculpture is coarser than in 

 other subspecies of B. concavus. The tergal side is abruptly bent 

 nearly at right angles with the rest of the valve, is deeply grooved, 

 but without nodes. The adductor ridge is strong but rather short. 



The tergum has a short, obliquely truncate spur. 



1 1 have seen some American Oligocene barnacles probably belonging to the concavus stock, but without 

 opercular valves. 



Prof. Gravel has recorded E. concavus as recent from Rio Janeiro, on the evidence of specimens in the 

 Paris Museum, collected by Delalande 1817. As there is no other Atlantic record, this requires confirma- 

 tion. See Nouv. Arch, du Mus., ser. 4, vol. 5, p. 130. 



