1914] 



English,: Agasoma-like Gastropods 



245 



Genus TROPHOSYCON Cooper 



This genus, of which Trophosycon Jcernianum is the type, was 

 originally proposed as a sub-genus of Agasoma. However, it seems 

 worthy of generic rank. Trophosycon is characterized by low conical 

 spire, large body-whorl, medium heavy shell, sub-oval mouth-opening, 

 an upper and lower angulation of the later whorls, spiral rows of nodes 

 along the lines of angulation, spiral and vertical ribbing, and very 

 wide, shallow, recurved canal. 



The group of extinct species which form this genus are closely 

 interrelated, but seem to have no very near relations among living 

 species. They are classed among the Doliidae on the basis of the re- 

 semblance of immature specimens to members of the genus Ficus, 

 which indicates a probable genetic relationship between the two . 



Genus AGASOMA Gabb 



Type Agasoma gravidum Gabb. This genus is defined by Gabb as 

 "sub-fusiform, spire low, body- whorl long; canal moderately produced 

 and slightly deflected ; aperture elongate ; labrum simple, labium en- 

 crusted with a thin, smooth plate; suture bordered as in Clavella. 

 . . . It differs [from Clavella] in the very short spire and in the short 

 and slightly curved canal. " The Agasoma species fall into two sections 

 capable of more precise definition. The first section includes only 

 Agasoma sinuatum, with narrow mouth opening; narrow, deep, medium 

 length, recurved canal ; and pronounced lower angulation of the body- 

 whorl. The second section includes the other species, with evenly 

 rounded, ventricose body-whorl, and shallow, wide canal. 



The large body- whorl, the shape of the canal, and the prominent 

 callus are similar to Trophosycon, but there are important differences 

 between the two genera, chiefly the presence of vertical ribs and nodes 

 on Trophosycon. Agasoma is retained in the Buccinidae, though it 

 represents a part of that family in which the shell shows some char- 

 acteristics of the Doliidae. 



FICUS MAMILLATTJS Gabb 



Finis mamillatus Gabb, Palae. Calif., vol. 1, p. 211, pi. 32, fig. 276, 1864. 

 Ficus mamillatus, Arnold, Smithsonian Misc. Coll., vol. 50, pt. 4, pi. 50, fig. 

 5, 5a, 1907. 



This species is listed by Gabb from the Tejon formation of Fort 

 Tejon, and by Arnold from the Topatopa formation ten miles south- 



