21 



radiately striated, spirally sulcatc; umbilicus wide, in 

 numerou-ly crenulated, umbilical \\nll \vilh :i spiral rili. 

 I)i:un. \} mill. 



8tr 



Ma-ilv known by the flatness of (he -hell :ind the two \ 

 prominent, ribs about the periphery. Hanley's figure of this 

 sprcies in Tlies. Couch, is a very poor representation. 



T. DiBOOiDiA, Pease. PI. <;. iig. o. 



Shell very depressed; whorls finely granulated, slightly chan- 

 neled at llit' suture, spirally snleate and ribbed, the two rib 

 the periphery being very strong ; color white, clouded with very 

 faint chocolate; base rounded, umbilicus lightly crenuhited, 

 channeled, umbilical wall with two spiral ribs. Diam. .'J mill. 



Paumotus. 

 T. ASPERA, Hinds. PL G, figs. 7, . 



Shell discoidal, slightly conical ; whorls rough, tubercular, 

 radiate! v striated, spirally snleate, strongly ribbed on the per- 

 iphery; base rounded, umbilicus very wide, its margin numer- 

 ously crenuhited. Diam. 94 mill. 



Strait* of Macassar. 



The type of this species was a dead shell and consequent!}'' 

 without color. 



T. ARCIJIT.E, Costa. PL 6, figs. 9, 10, 11. 



Shell discoidal ; whorls flat above, rounded below, channeled 

 at the suture, longitudinally and spirally sulcate, crenellated ; 

 color yellowish white ; umbilicus veiy wide, margin finely crenu- 

 hited. Diam. 7'5 mill. 



Mediterranean. 

 T. SOWERBVI, Ilanlcy. PL G, figs. 12, 13. 



Shell nearly discoidal; whorls channeled at the suture, with 

 four granosc tMiiguhi', the upper three of which are equal and the 

 fourth greater, last whorl with 13-14 cinguhe. periphery sloping 

 off, not biangulute ; color yellowish white, clouded or vari< gated ; 

 umbilicus moderate, its margins erenulated. Diam. '. mill. 



Mo i in, Tun in. 



This species is distinguished from the preceding by the much 

 more narrow umbilicus. 



