12 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



In Paldeocreusia devonica J. M. Clarke, from the Corniferous lime- 

 stone of New York, 1 the form is practically that of Pyrgoma. It is 

 embedded in a Favosites colony, which has also overgrown the upper 

 surface. No compartments are visible and no opercular valves 

 found. While the fossil presents no characters differentiating it from 

 the modern Pyrgoma, yet it is also utterly without features definitely 

 placing it in the Cirripedia. The question is not whether Palxocreusia 

 is a close relative of Creusia this is practically excluded by the fact 

 that Creusia and Pyrgoma are highly specialized forms of the most 

 recent family of barnacles but whether it is a cirripede at all. 



CLASSIFICATION. 



The modern classification of cirripedes began with Leach, who, in 

 1825, proposed the folio whig arrangement. I add the contents of 

 the families in brackets: 



Class CIRRIPEDES. 

 Order 1. Campylosomata. 

 Family Clytiadse [Conchoderma]. 



Pollieipedidae [Lepas, Scalpdlem, Pollicipes, etc.] 

 Ibladte [Ibla]. 

 Order 2. Acamptosomata. 

 Family Coronuladte [Tubicinella, Coronula, Chelonibia]. 



Balanidse [Pyrgoma, Acasta, Balanus, Tetradlta, Eliminus, etc.]. 

 Clistadte [ Verruca]. 



Darwin revised this classification in 1852-1854. His chief addi- 

 tions to the system of sessile barnacles were the demonstration of 

 important differences in the morphology of the turtle barnacles 

 (CTielonibia) and the whale barnacles, and the separation of the 

 Chthamalinae from the Balaninae. In addition to this, he estab- 

 lished the genera upon sound morphological characters, demonstrated 

 their affinities with wonderful insight, and denned the species, which 

 had before been in the greatest confusion. Darwin's monograph has 

 been the basis of all subsequent systematic work, and is still the 

 chief work of reference. 



The family and generic classification of this work is substantially 

 that of Darwin. The principal departures are that the turtle barna- 

 cles are removed from the Balanihse to form a separate subfamily; 

 the arrangement of the Coronulinse is altered, considerable changes 

 have been made in the subgeneric arrangement of the Balani, and the 

 grade of supergeneric groups has been raised. I consider Darwin's 

 subfamilies as families, and his primary divisions of subfamilies may 

 then be ranked as subfamilies. Such an alteration of taxonomic 

 values has been general throughout zoology during the last half cen- 

 tury. It should in no way obscure the fact that the system of the 

 Cirripedia Thoracica is still essentially Darwinian. 



1 Palaeontology of New York, vol. 7, 1888, p. 210, pi. 30, figs. 24-2(5. 



