248 BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



Genus TETRACLITA Schumacher. 



1817. Tetrnclita Schumacher, Essai d'un nouveau Systeme des Habitations 

 des Vers testac6s, p. 91, type T. squaniulosa Scliuniaclier=T. squamosa 

 Bruguiere. 



1817. Con id. Leach, Journal de Physique, vol. 85, p. 69, monotype C. porosa. 

 {Monoloinis Klein stated to be the same.) 



1817. Ascmus Ranzani, Opuscoli sciontifici, vol. 1, p. 27.'5, no species men- 

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



1822. Polytrcma Fekussac, Dictionnaire classique d'Hlstoire Naturelle, vol. 

 2, p. 144 {Balanus stalactiferus Lamarcli and squamosns Bruguiere). 



Balanitis with four compartments, sometimes externally calci- 

 fied 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. 



Tef7YicUfa and the allied genera Ehnlnius, Creush., and Pyrgomd 

 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 CoJiopca, and are 

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

 other tetramerous genera it appears that a parallel modification has 

 taken place. There is a striking resemblance between Tetraclita and 

 Semihalamis, 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 Eanzani recognized and gave names to 

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

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

 by all subsequent zoologists mentioning the group. 



My field experience with Tetraclita is limited to southern Florida, 

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

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

 association with C hthamalus I presume that it is also a surf barnacle 

 elscAvhere. Tetraclita has its greatest development in the Philippines 

 and Mala,y 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 tyj)e was from a ship in Boston Bay. One 



