248 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



Genus TETRACLITA Schumacher. 



1817. TetracUta SCHUMACHER, Essai d'un nouveau Systeme des Habitations 

 des Vers testaces, p. 91, type T. squamulosa Schumacher=T. squamosa 

 Brugui&re. 



1817. Conia LEACH, Journal de Physique, vol. 85, p. 69, monotype C. porosa. 

 (Monolopus Klein stated to be the same.) 



1817. Asemus RANZANI, Opuscoli scientific!, vol. 1, p. 275, no species men- 

 tioned; also vol. 2, 1818, p. 64, for A. porosus (=Lepas porosa Gmelin). 



1822. Polytrcma FEKUSSAC, Dictionnaire classique d'Histoire Naturelle, vol. 

 2, p. 144 (Balanus stalactifcrus Lamarck and squam-osus Bruguiere). 



Balanidse with four compartments, sometimes externally calci- 

 ned together ; parietes permeated by pores, generally forming several 

 irregular rows; radii either developed or obsolete. Basis flat, irreg- 

 ular, calcareous, or thin or membranous. Labrum notched in the 

 middle. 



Type. T. squamosa (Bruguiere). 



Distribution. All tropical and warm temperate seas, in the lit- 

 toral zone. 



TetracUta and the allied genera Elminius, Creusia, and Pyrgoma 

 are apparently to be regarded as Balanoid barnacles which have lost 

 the carinolateral compartments. These compartments tend to dis- 

 appear in some hexamerous barnacles. They are very narrow and 

 do not reach the base in some species of Acasta and Conopca, and are 

 wanting in Balanus (Conopea) cornuta. In TetracUta and several 

 other tetramerous genera it appears that a parallel modification has 

 taken, place. There is a striking resemblance between TetracUta and 

 /Semibalanus, possibly indicating some affinity. Both have a tendency 

 to subdivide the parietal pores, and in both the internal lamina of 

 the wall is ribless. 



When radii are undeveloped there are still vermiculate ridges 

 representing the septa of the radial edges. These are represented in 

 plate 61, figure le. 



Schumacher, Leach, and Ranzani recognized and gave names to 

 this generic group in the same year. It is not known which actually 

 published first, but the name given by Schumacher has been preferred 

 by all subsequent zoologists mentioning the group. 



My field experience with TetracUta is limited to southern Florida, 

 Cuba, and California, where it is an intertidal barnacle, living in a 

 zone above any Balanus of the same localities. From its frequent 

 association with Ckthamalus I presume that it is also a surf barnacle 

 elsewhere. TetracUta has its greatest development in the Philippines 

 and Malay Archipelago. 



The following three forms are not represented in the National 

 Museum collections : 



T. squamosa, patellaris Darwin (T. porosa var. patellaris Darwin, 

 Monograph, p. 330) . The type was from a ship in Boston Bay. One 



