THE SESSILE BARNACLES. 235 



" Pariotes and basis sometimes permeated by pores, sometimes not ; 

 radii not permeated by pores. Shell elongated in its rostyocarinal 

 axis; basis hoat-shaped [or compressed conic]. Attached to Gor- 

 goniffi and Millepora>." (Darwin). Radii well developed. 



Type. — C. elongata Say=Balanus galeatus (Linnaeus) Darwin. 



Distribution. — Tropical and warm temperate seas in both hemi- 

 spheres, from above low tide to over 200 fathoms. 



This group was thought by Darwin to have affinities with the 

 subgenus now called Megahalanus., and wdth Acasta. Hoek places it 

 at the end of Balanus, after the groups wdth poreless compartments. 

 The characters of the cirri favor this view. The segments of the 

 first and second cirri are not protuberant, and in some species the 

 fourth cirrus bears some short spinules, reminiscent of those of 

 Acasta. 



I haA'e been unable to decide whether the species of Conopea with 

 poreless compartments are secondarily so by reason of the filling 

 up of pores solidly, or whether, like Acasta, parietal pores have 

 never been evolved. It is possible, though it does not appear prob- 

 able, that the group is diphyletic, composed of one series of species 

 related to the poreless Balani and Acasta^ and another related to 

 the porous Balani. I have been able to study only B. galeatus, 

 B. calceohis, and B. scandens. 



B. cornutus is remarkable for the abortion of the carinolateral 

 compartments. It is the only Balanus having but four compart- 

 ments. 



Lepas cassis Spengler^ is a Balanus growing on a gorgonian as 

 the Conopeas grow. It can probably be recognized if found again. 



Conopea contains nine species, enumerated below. They are not 

 well-known barnacles, as excepting B. galeatus, the species are known 

 by but few specimens in museums. The Malay Archipelago is the 

 center of speciation. Only two species are known to occur in the 

 Atlantic. Those represented in the United States National Museum 

 are starred in the following list. 



B. stultus Darv\'in, 1851. Singapore. 



*B. calceolus Darwin, 1854. West coast of Africa; Tuticorin; 

 MaLnfy Archipelago ; Coralline Crag of Britain. 



B. investitiis Hoek, 1913. Flores Sea. 



*5. galeatus Linnajus. West Indies; Southern California. 



B. navicula Darwin, 1854. Tuticorin; Malay Archipelago. 



B. cornutus Hoek, 1913. Malay Archipelago. 



B. cymhiforniis Darwin, 1854. Tuticorin, near Madras. 



B. proripiens Hoek, 1913. Malay Archipelago. 



* B. scandens Pilsbry. Japan. 



1 Skrivter af Natiirhistorie Selskabet, vol. 1, 1790, p. 184, pi. 6, fig. 3a, b. 



