334 BULLETIN 03, UNITED STATES NATIONAL MUSEUM. 



Genus OCTOMERIS Sowerby. 



1S25. Octomeris SOWEEBY, Zoological Journal, vol. 2, p. 244. Monotype, O. 



angulosa. 

 1854. Octomeris Sowerby, DARWIN, Monograph, p. 282. 



Chthamalidce with eight compartments; edges of the radii crenated; 

 basis membranous. 



Darwin describes two species, O. angulosa Sowerby, from Algoa 

 Bay, South Africa, and O. brunnea Darwin, from the Philippines. 

 No others have been described since his monograph. They inhabit 

 the littoral zone. 



OCTOMERIS ArGULOSA Sowerby. 



1854. Oclomrrift angulosa Sowerby, DARWIN, Monograph, p. 483, pi. 20, figs. 

 2a, 2b. 



The Cape Town specimens have deeply cut, continuous ribs, such 

 as are shown in Chenu's figures of "Octomeris augubra" This form 

 may, perhaps, be separable from the typical O. anyulosa-, but my 

 material is not abundant enough for a decision. Chenu's name was 

 probably an error of the engraver and not intended as a new name. 



Genus CATOPHRAGMUS Sowerby. 

 1S27. Catophragmus SOWERBY, Genera of Recent and Fossil Shells. 

 1854. Cato-pJiragmus Sowerby, DARWIN, Monograph, p. 485. 



Interior compartments eight, provided with alfe but no radii; 

 their bases concealed by one or several exterior whorls of small, 

 supplemental compartments ; basis either membranous or calcareous ; 

 scutum without an adductor ridge, the articular ridges of both valves 

 strongly developed. Caudal appendages present in some species. 



The three species of this genus are about as widely separated as 

 possible, one littoral species on the eastern coast of Australia, another 

 in the West Indies, and the third in deep water of the Hawaiian 

 Archipelago. They are evidently the remnants of an ancient group. 

 In structure they are rather divergent. I have not seen C. imbricatus, 

 but the other two species differ markedly in texture. C. polymerus 

 has a great deal of chitin in the compartments, and the calcareous 

 material is partly purplish. C. darwini is conspicuously porcellanous 

 and dead white. 



