THE SESSILE BARNACLES. 335 



KEY TO SUBGENERA AND SPECIES. 



a 1 . Caudal appendages wholly wanting; basis membranous; basal edges of 

 the inner compartments beveled outside, the outer layer not extending to 

 the base ; supplementary compartments numerous, carinate, imbricating 

 over the sutures of each preceding whorl. Subgenus Catomcrus (new 



subgenus) C. polymcrus Darwin. 



a'. Caudal appendages present. 



b 1 . Basis calcareous ; supplementary compartments not keeled, not very 

 numerous, imbricating over the sutures ; white ; caudal appendages very 



small. Subgenus Catopliragmus C. imbricatus Sowerby. 



b\ Basis unknown ; basal edges of the inner compartments not beveled out- 

 side, the outer layer extending to the base; supplementary compart- 

 ments in a single series, not restricted to the sutures of the inner wall, 

 and of several forms, with or without one or two alse ; white and por- 

 cellanous in texture ; caudal appendages well developed. Subgenus 

 Chionelasmns Pilsbry C. darwini Pilsbry. 



CATOPHRAGMUS IMBRICATUS Sowerby. 



1827. CatopJiragmus imbricatus SOWERBY, Genera of Recent and Fossil 



Shells. 



1S54. CatopJiragmus imbricatus Sowerby, DARWIN, Monograph, p. 490. 

 1901. Catopliragmus imbricatus Sowerby, VERRILL, Trans. Conn. Acad., vol. 



11, pt. 1, p. 22, pi. S, figs. 8, 9. 



Type. British Museum, from Antigua. 



Distribution. Antillean faunal province; Antigua and Bermuda. 



This species is not contained in the National Museum. It is dis- 

 tinguished from C. polyinerus by the white color, the calcareous basis 

 and the caudal appendages, which, according to Darwin, are short, 

 equaling only the lower segment of the pedicel of the sixth cirrus, 

 and consisting of three joints, in a young specimen 5 mm. in dia- 

 meter. It attains a diameter of three-quarters of an inch, according 

 to Darwin. Professor Verrill remarks of those found by him in 

 Bermuda : 



Several specimens of this interesting barnacle were found on littoral rocks. 

 They are all young (about 5 to 8 mm. in diameter) and agree well with the 

 young one described by Darwin from Antigua. The eight primary mural 

 plates are pointed and surrounded and partially concealed by about three 

 alternating whorls of smaller, pointed plates; rapidly decreasing in size ex- 

 teriorly. The opercular scuta are strongly concentrically ribbed and have a 

 deep, median radial sulcus. The base is calcareous, but thin. The color is 

 pure white. 



CATOPHRAGMUS DARWINI Pilsbry. 



1907. Catopliragmus darwini PILSBRY, Bulletin of the Bureau of Fisheries, 

 vol. 26, p. 188, fig. 4, pi. 5, figs. 1-8. 



1911. Catopliragmus (Chionelastmis) darwini PILSBEY, Bull. Bur. of Fish- 

 eries, vol. 29, p. 82. 



Type. Cat. Nos. 32407, 32408, U.S.N.M. 



Distribution. Hawaiian Islands: Albatross station 30J)8, vicinity 

 of Kauai, in 228 to 235 fathoms. 



