THE SESSILE BARNACLES. 249 



specimen in the collection of the Academy of Natural Sciences, Phila- 

 delphia, was from a ship from the East Indies. It is volcano-shaped, 

 Avith very small orifice ; scutum thin, with rather weak crests for the 

 lateral depressor muscle; tergum small and extremely narrow. 



T, mitra {Lepas mltra Spengler, Skrivter af Naturhistorie Selska- 

 bet, vol. 1, 1790, p. 192, pi. G, fig. 5. From " Niquebar"). 



T. serrata Darwin (IMonograph, p. 334) , South Africa. Close to T. 

 sqnmnosa^ but the articular and adductor ridges are united above, 

 inclosing a. " cavity which runs to the apex of the valve." Weltner 

 and Kriiger state that there are forms intermediate between serrata 

 and squamosa-. This species could not be distinguished by the char- 

 acters given in the keys of Iloek and Gruvel. These keys are also 

 otherwise impracticable. 



T. purpurascens Wood (Darwin, Monograph, p. 342). Synonyms: 

 B alarms pVtcatiis Lamarck. Conia depressa Gray. Australia ; New 

 Zealand. 



TETRACLITA SQUAMOSA (BruguiSre). 



17S9. Balanus squamosus BKUGUifiRE, Encyclopedie IMetliodique, p. 170. 



1790. Lepas Junyites Spengler, Skrivter af Naturhistorie Selskabet, vol. 

 1, p. 189. 



1791. Lepas porosa Gxielin, Systema Naturae, ed. 13, p. 3212. 



1S17. Tetraclita sqitaintdosa Schl'macher, Essai d'uu uouv. Syst. Vers 



Testae, p. 91. 

 1854. Tetraclita pcyrosa Gmelin, Daewin, in part. Monograph, p. 329, pi. 



10, figs. lf/-l//(, witli varieties communis, nigresccns, viridis, ruhescens, 



and p. 330, var. elcgans, pateUaris. 

 1900. Tetraclita porosa (Ouielin) var. viridis i;>arwin, Borradaile, Proc. 



Zool. Soc, London, p. 799 (Rotuiua). 



Distrihut'/on. — World-wide in tropical and subtropical seas; dis- 

 tribution of the tj'pical form, Japan, coast of China, Philippines, 

 and the Malay Archipelago.^ 



Six varieties of this species were defined by Darwin. As in the 

 cases of Balanus tlntinnaljulum and B. amphltrlte^ he at first thought 

 to rank several of them as distinct species, but w^as deterred by find- 

 ing various forms uniting characters of two varieties. After study- 

 ing some hundreds of specimens I am much disposed to rank as 

 species T. ruhescens and stalact'ifera in America, and T. squatnosa^ 

 japonica, and rufotincta in the Old World. While they are varia- 

 ble, I have no reason to think that any of these races intergrade. 

 Yet as the forms of India, South Africa, and Australia are unknown 

 to me, such a course might Ijc premature. Moreover, I have not been 

 able to find time for a thorough examination of the cirri and mouth 

 parts of the several races. 



' Doctor Kriiger tias reported T. porosa var. viridii from Sagami Bay, Japan, and the Pescadores, and 

 has figured the tergum and six scuta. The form of the tergum is somewhat unlike the Cliinese and Pliil- 

 Ippine specimens I have seen. 



