S34 BULLETIN 9.3^ UNITED STATES NATIONAL MUSEUM. 



Genus OCTOMERIS Sowerby. 



1825. Octomcris Sowerby, Zoological .Tournal, vol. 2, p. 244. Monotype, O. 



angulosa. 

 1S54. Octomcris Sowerby, D^vrwin, Monograph, p. 282. 



Chthaitial'idm with eight compartments ; edges of the radii crenated ; 

 basis membranous. 



Darwin desci-ibes two species, 0. angulosa Sowerby, from Algoa 

 Bay, South Africa, and 0. brunnea Darwin, from the Philippines. 

 No others have been described since his monograph. They inliabit 

 the littoral zone. 



OCTOMERIS AFGULOSA Sowerby. 



1854. Octomeris anf/ulosa Sowerby, Dabwin, Monograph, p. 483, pi. 20, figs. 

 2(t, 2b. 



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

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

 ma}^, perhaps, bo separable from the typical 0. angulosa.^ but my 

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

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



Genus CATOPHRAGMUS Sowerby. 

 1827. CdtopJirdf/inuft Sowerby, Genera of Recent and Fossil Shells. 

 1854. Cdtophragiinis Sowerby, Darwin, Monograph, p. 485. 



Interior compartments eight, provided with alse 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 xVustralia, 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 stiiicture tliey are rather divergent. I have not seen C. imhrlcatus, 

 but the other two species differ markedly in texture. 0. poh/menis 

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

 material is jiartly purplish. ('. darwinl is conspicuously porcellanous 

 and dead white. 



