362 PROCEEDINGS OF THE ACADEMY OF [PaRT II 



nupera (Conrad), ^^ which varies so markedly toward Cassis (Pho- 

 lium) hrevicostatus Conr., that it is evident the two are but shghtly 

 divergent mutations of a common ancestor. In S. nupera the den- 

 ticulation of the hp and columella is but weakly developed; varices 

 are present but not strong; the columellar callus is adnate, the si- 

 phon as much recurved as in some Eocene species of Phalium, and 

 the siphonal fasciole moderately prominent. The initial whorl 

 is smaller than in later forms, but the whole embryonic shell is 

 more globose. A direct descendant of S. nupera appears to be S. 

 hodgei Conr., in the Miocene of Duplin Co., North Carolina, which 

 is modified chiefly by the loss of a convex siphonal fasciole. 



A lateral branch from S. nupera leads to S. liniea Conr., of the 

 Vicksburg Oligocene, which differs from the parent stock mainly in 

 the more slender embryonic shell. From S. liniea probably arose 

 S. laevigata Sowb.,of the Santo Domingo beds, and S. suhlaevigata 

 Guppy, of the still later Bowden bed. The latter leads directly to 

 the recent Antillean S. striata through the intermediate Pliocene 

 form of Costa Rica. 



Sconsia therefore branched from the Phalium stock of Cassididae 

 in the early Eocene, and its progress has been marked by the re- 

 duction of the columellar callus, shortening of the anterior siphon 

 and loss of a convex siphonal fasciole. It is not allied to Morio, as 

 Fischer held. 



The mutation series may be graphically represented thus : 

 Recent, Antillean Province S. striata. . . .C. inflata & var. granulosa 



Pliocene, Costa Rican S. striata suhlaevigata C. inflata granulosa 



Miocene, S. hodgei i C. caelata 



I Bowden . 



1 Santo Domingan. 



Oligocene, Vicksburgian . 



<S. striata suhlaevigata 

 S. I. laevigata 



S. lintea. 



C. inflata monilif era 

 . C. inflata monilif era 



. . .C. caelatura 



Eocene, Claibornian. .»S. nupera -\-hrevicosiata. .C. taitii 



\ / I 



Subgenus Sconsia — Subgenus Phalium 



On the right side, the ancestry of the modern Cassis (Phalium) 

 inflata is indicated, but with no attempt to arrange the other species, 



^^ Cassis miperus Conr., Fossil Shells of the Tertiary Formations of North Am- 

 erica. Vol. I, no. 4, p. 46, October 1833. Buccinum sowerbyi Lea, Cont. to Geol. 

 p. 164, PI. F) f. 169, Dec. 1833. Sernicassis nuperus Conr., Amer. Jour. Conch. 

 Vol. I, p. 26, 186.5. 



